Interrupt List, part 3 of 8
This compilation is Copyright (c) 1989,1990,1991,1992 Ralf Brown
----------20---------------------------------
INT 20 - Minix - SEND/RECEIVE MESSAGE
AX = process ID of other process
BX -> message
CX = 1 send
2 receive
3 send&receive
Note: the message contains the system call number (numbered as in V7
Unix(tm)) and the call parameters
----------20---------------------------------
INT 20 - DOS 1+ - TERMINATE PROGRAM
CS = PSP segment
Return: never
Note: (see INT 21/AH=00h)
SeeAlso: INT 21/AH=00h,INT 21/AH=4Ch
----------2100-------------------------------
INT 21 - DOS 1+ - TERMINATE PROGRAM
AH = 00h
CS = PSP segment
Notes: Microsoft recomments using INT 21/AH=4Ch for DOS 2+
execution continues at address stored in INT 22 after DOS performs
whatever cleanup it needs to do
if the PSP is its own parent, the process's memory is not freed; if
INT 22 additionally points into the terminating program, the
process is effectively NOT terminated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=26h,AH=31h,AH=4Ch,INT 20,INT 22
----------2101-------------------------------
INT 21 - DOS 1+ - READ CHARACTER FROM STANDARD INPUT, WITH ECHO
AH = 01h
Return: AL = character read
Notes: ^C/^Break are checked, and INT 23 executed if read
character is echoed to standard output
standard input is always the keyboard and standard output the screen
under DOS 1.x, but they may be redirected under DOS 2+
SeeAlso: AH=06h,AH=07h,AH=08h,AH=0Ah
----------2102-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO STANDARD OUTPUT
AH = 02h
DL = character to write
Return: AL = last character output (despite the official docs which state
nothing is returned) (at least DOS 3.3-5.0)
Notes: ^C/^Break are checked, and INT 23 executed if pressed
standard output is always the screen under DOS 1.x, but may be
redirected under DOS 2+
the last character output will be the character in DL unless DL=09h
on entry, in which case AL=20h as tabs are expanded to blanks
SeeAlso: AH=06h,AH=09h
----------2103-------------------------------
INT 21 - DOS 1+ - READ CHARACTER FROM STDAUX
AH = 03h
Return: AL = character read
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDAUX is usually the first serial port
SeeAlso: AH=04h,INT 14/AH=02h,INT E0/CL=03h
----------2104-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO STDAUX
AH = 04h
DL = character to write
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDAUX is usually the first serial port
if STDAUX is busy, this function will wait until it becomes free
SeeAlso: AH=03h,INT 14/AH=01h,INT E0/CL=04h
----------2105-------------------------------
INT 21 - DOS 1+ - WRITE CHARACTER TO PRINTER
AH = 05h
DL = character to print
Notes: keyboard checked for ^C/^Break, and INT 23 executed if detected
STDPRN is usually the first parallel port, but may be redirected under
DOS 2+
if the printer is busy, this function will wait
SeeAlso: INT 17/AH=00h
----------2106-------------------------------
INT 21 - DOS 1+ - DIRECT CONSOLE OUTPUT
AH = 06h
DL = character (except FFh)
Return: AL = character output (despite official docs which state nothing is
returned) (at least DOS 3.3-5.0)
Notes: does not check ^C/^Break
writes to standard output, which is always the screen under DOS 1.x,
but may be redirected under DOS 2+
SeeAlso: AH=02h,AH=09h
----------2106--DLFF-------------------------
INT 21 - DOS 1+ - DIRECT CONSOLE INPUT
AH = 06h
DL = FFh
Return: ZF set if no character available
ZF clear if character available
AL = character read
Notes: ^C/^Break are NOT checked
if the returned character is 00h, the user pressed a key with an
extended keycode, which will be returned by the next call of this
function
reads from standard input, which is always the keyboard under DOS 1.x,
but may be redirected under DOS 2+
SeeAlso: AH=0Bh
----------2107-------------------------------
INT 21 - DOS 1+ - DIRECT CHARACTER INPUT, WITHOUT ECHO
AH = 07h
Return: AL = character read from standard input
Notes: does not check ^C/^Break
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), partially-formed
double-byte characters may be returned
SeeAlso: AH=01h,AH=06h,AH=08h,AH=0Ah
----------2108-------------------------------
INT 21 - DOS 1+ - CHARACTER INPUT WITHOUT ECHO
AH = 08h
Return: AL = character read from standard input
Notes: ^C/^Break are checked, and INT 23 executed if detected
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), partially-formed
double-byte characters may be returned
SeeAlso: AH=01h,AH=06h,AH=07h,AH=0Ah,AH=64h
----------2109-------------------------------
INT 21 - DOS 1+ - WRITE STRING TO STANDARD OUTPUT
AH = 09h
DS:DX -> '$'-terminated string
Return: AL = 24h (the '$' terminating the string, despite official docs which
state that nothing is returned) (at least DOS 3.3-5.0)
Notes: ^C/^Break checked, and INT 23 called if pressed
standard output is always the screen under DOS 1.x, but may be
redirected under DOS 2+
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=02h,AH=06h"OUTPUT"
----------210A-------------------------------
INT 21 - DOS 1+ - BUFFERED INPUT
AH = 0Ah
DS:DX -> buffer (see below)
Return: buffer filled with user input
Notes: ^C/^Break checked, and INT 23 called if detected
reads from standard input, which may be redirected under DOS 2+
if the maximum buffer size (see below) is set to 00h, this call returns
immediately without reading any input
SeeAlso: AH=0Ch,INT 2F/AX=4810h
Format of input buffer:
Offset Size Description
00h BYTE maximum characters buffer can hold
01h BYTE (input) number of chars from last input which may be recalled
(return) number of characters actually read, excluding CR
02h N BYTEs actual characters read, including the final carriage return
----------210A00-----------------------------
INT 21 - WCED v1.6 - INSTALLATION CHECK
AX = 0A00h
DS:DX -> 6-byte buffer whose first two bytes must be 00h
Return: buffer offset 02h-05h filled with "Wced" if installed
Note: WCED is a free command-line editor and history utility by Stuart
Russell
SeeAlso: AH=FFh"CED"
----------210B-------------------------------
INT 21 - DOS 1+ - GET STDIN STATUS
AH = 0Bh
Return: AL = 00h if no character available
= FFh if character is available
Notes: ^C/^Break checked, and INT 23 called if pressed
standard input is always the keyboard under DOS 1.x, but may be
redirected under DOS 2+
if the interim console flag is set (see AX=6301h), this function
returns AL=FFh if a partially-formed double-byte character is
available
SeeAlso: AH=06h"INPUT",AX=4406h
----------210B56-----------------------------
INT 21 - VIRUS - "Perfume" - INSTALLATION CHECK
AX = 0B56h
Return: AX = 4952h if resident
SeeAlso: AX=0D20h
----------210C-------------------------------
INT 21 - DOS 1+ - FLUSH BUFFER AND READ STANDARD INPUT
AH = 0Ch
AL = STDIN input function to execute after flushing buffer
other registers as appropriate for the input function
Return: as appropriate for the specified input function
Note: if AL is not one of 01h,06h,07h,08h, or 0Ah, the buffer is flushed but
no input is attempted
SeeAlso: AH=01h,AH=06h"INPUT",AH=07h,AH=08h,AH=0Ah
----------210D-------------------------------
INT 21 - DOS 1+ - DISK RESET
AH = 0Dh
Notes: writes all modified disk buffers to disk, but does not update directory
information (that is only done when files are closed or a SYNC call
is issued)
SeeAlso: AX=5D01h,INT 13/AH=00h,INT 2F/AX=1120h
----------210D20-----------------------------
INT 21 - VIRUS - "Crazy Imp" - INSTALLATION CHECK
AX = 0D20h
Return: AX = 1971h if resident
SeeAlso: AX=0B56h,AH=30h/DX=ABCDh
----------210E-------------------------------
INT 21 - DOS 1+ - SELECT DEFAULT DRIVE
AH = 0Eh
DL = new default drive (00h = A:, 01h = B:, etc)
Return: AL = number of potentially valid drive letters
Notes: under Novell NetWare, the return value is always 32, the number of
drives that NetWare supports
under DOS 3+, the return value is the greatest of 5, the value of
LASTDRIVE= in CONFIG.SYS, and the number of drives actually present
on a DOS 1.x/2.x single-floppy system, AL returns 2 since the floppy
may be accessed as either A: or B:
otherwise, the return value is the highest drive actually present
DOS 1.x supports a maximum of 16 drives, 2.x a maximum of 63 drives,
and 3+ a maximum of 26 drives
SeeAlso: AH=19h,AH=3Bh,AH=DBh
----------210F-------------------------------
INT 21 - DOS 1+ - OPEN FILE USING FCB
AH = 0Fh
DS:DX -> unopened File Control Block (see below)
Return: AL = status
00h successful
FFh file not found or access denied
Notes: (DOS 3.1+) file opened for read/write in compatibility mode
an unopened FCB has the drive, filename, and extension fields filled
in and all other bytes cleared
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=10h,AH=16h,AH=3Dh
Format of File Control Block:
Offset Size Description
-7 BYTE extended FCB if FFh
-6 5 BYTEs reserved
-1 BYTE file attribute if extended FCB
00h BYTE drive number (0 = default, 1 = A, etc)
01h 8 BYTEs blank-padded file name
09h 3 BYTEs blank-padded file extension
0Ch WORD current block number
0Eh WORD logical record size
10h DWORD file size
14h WORD date of last write (see AX=5700h)
16h WORD time of last write (see AX=5700h) (DOS 1.1+)
18h 8 BYTEs reserved (see below)
20h BYTE record within current block
21h DWORD random access record number (if record size is > 64 bytes, high
byte is omitted)
Note: to use an extended FCB, you must specify the address of the FFh flag at
offset -7, rather than the address of the drive number field
Format of reserved field for DOS 1.0:
Offset Size Description
16h WORD location in directory (if high byte = FFh, low byte is device
ID)
18h WORD number of first cluster in file
1Ah WORD current absolute cluster number on disk
1Ch WORD current relative cluster number within file
(0 = first cluster of file, 1 = second cluster, etc.)
1Eh BYTE dirty flag (00h = not dirty)
1Fh BYTE unused
Format of reserved field for DOS 1.10-1.25:
Offset Size Description
18h BYTE bit 7: set if logical device
bit 6: not dirty
bits 5-0: disk number or logical device ID
19h WORD starting cluster number on disk
1Bh WORD current absolute cluster number on disk
1Dh WORD current relative cluster number within file
1Fh BYTE unused
Format of reserved field for DOS 2.x:
Offset Size Description
18h BYTE bit 7: set if logical device
bit 6: set if open???
bits 5-0: ???
19h WORD starting cluster number on disk
1Bh WORD ???
1Dh BYTE ???
1Eh BYTE ???
1Fh BYTE ???
Format of reserved field for DOS 3.x:
Offset Size Description
18h BYTE number of system file table entry for file
19h BYTE attributes
bits 7,6: 00 = SHARE.EXE not loaded, disk file
01 = SHARE.EXE not loaded, character device
10 = SHARE.EXE loaded, remote file
11 = SHARE.EXE loaded, local file
bits 5-0: low six bits of device attribute word
---SHARE.EXE loaded, local file (DOS 3.x and 5.0)---
1Ah WORD starting cluster of file on disk
1Ch WORD (DOS 3.x) offset within SHARE of sharing record (see AH=52h)
(DOS 5.0) unique sequence number of sharing record
1Eh BYTE file attribute
1Fh BYTE ???
---SHARE.EXE loaded, remote file---
1Ah WORD number of sector containing directory entry
1Ch WORD relative cluster within file of last cluster accessed
1Eh BYTE absolute cluster number of last cluster accessed
1Fh BYTE ???
---SHARE.EXE not loaded---
1Ah BYTE (low byte of device attribute word AND 0Ch) OR open mode
1Bh WORD starting cluster of file
1Dh WORD number of sector containing directory entry
1Fh BYTE number of directory entry within sector
Note: if FCB opened on character device, DWORD at 1Ah is set to the address
of the device driver header, then the BYTE at 1Ah is overwritten.
----------2110-------------------------------
INT 21 - DOS 1+ - CLOSE FILE USING FCB
AH = 10h
DS:DX -> File Control Block (see AH=0Fh)
Return: AL = status
00h successful
FFh failed
Notes: a successful close forces all disk buffers used by the file to be
written and the directory entry to be updated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=16h,AH=3Eh
----------2111-------------------------------
INT 21 - DOS 1+ - FIND FIRST MATCHING FILE USING FCB
AH = 11h
DS:DX -> unopened FCB (see AH=0Fh), may contain '?' wildcards
Return: AL = status
00h successful
[DTA] unopened FCB for first matching file
FFh no matching filename, or bad FCB
Notes: the type of the returned FCB depends on whether the input FCB was a
normal or an extended FCB
for extended FCBs with search attribute 08h, the volume label (if any)
will be returned even if the current directory is not the root dir.
DOS 3+ also allows the '*' wildcard
the search FCB must not be modified if AH=12h will be used to continue
searching; DOS 3.3 has set the following parts of the FCB:
0Ch BYTE ???
0Dh WORD directory entry number of matching file
0Fh WORD cluster number of current directory
11h 4 BYTEs ???
15h BYTE drive number (1=A:)
at least for DOS 3.3, the unopened FCB in the DTA is actually the drive
number followed by the file's directory entry
SeeAlso: AH=12h,AH=1Ah,AH=4Eh,INT 2F/AX=111Bh
----------2112-------------------------------
INT 21 - DOS 1+ - FIND NEXT MATCHING FILE USING FCB
AH = 12h
DS:DX -> unopened FCB (see AH=0Fh)
Return: AL = status
00h successful
[DTA] = unopened FCB
FFh no more matching filenames
Note: (see AH=11h)
assumes that successful FindFirst executed on search FCB before call
SeeAlso: AH=1Ah,AH=4Fh,INT 2F/AX=111Ch
----------2113-------------------------------
INT 21 - DOS 1+ - DELETE FILE USING FCB
AH = 13h
DS:DX -> unopened FCB (see AH=0Fh), filename filled with template for
deletion ('?' wildcards allowed)
Return: AL = status
00h one or more files successfully deleted
FFh no matching files or all were read-only or locked
Notes: DOS 1.25+ deletes everything in the current directory (including
subdirectories) and sets the first byte of the name to 00h (entry
never used) instead of E5h if called on an extended FCB with
filename '???????????' and bits 0-4 of the attribute set (bits 1 and
2 for DOS 1.x). This may have originally been an optimization to
minimize directory searching after a mass deletion (DOS 1.25+ stop
the directory search upon encountering a never-used entry), but can
corrupt the filesystem under DOS 2+ because subdirectories are
removed without deleting the files they contain.
currently-open files should not be deleted
SeeAlso: AH=41h,INT 2F/AX=1113h
----------2114-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL READ FROM FCB FILE
AH = 14h
DS:DX -> opened FCB (see AH=0Fh)
Return: AL = status
00h successful
01h end of file (no data)
02h segment wrap in DTA
03h end of file, partial record read
[DTA] = record read from file
Notes: reads a record of the size specified in the FCB beginning at the
current file position, then updates the current block and current
record fields in the FCB
if a partial record was read, it is zero-padded to the full size
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=15h,AH=1Ah,AH=3Fh,INT 2F/AX=1108h
----------2115-------------------------------
INT 21 - DOS 1+ - SEQUENTIAL WRITE TO FCB FILE
AH = 15h
DS:DX -> opened FCB (see AH=0Fh)
[DTA] = record to write
Return: AL = status
00h successful
01h disk full
02h segment wrap in DTA
Notes: writes a record of the size specified in the FCB beginning at the
current file position, then updates the current block and current
record fields in the FCB
if less than a full sector is written, the data is placed in a DOS
buffer to be written out at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=14h,AH=1Ah,AH=40h,INT 2F/AX=1109h
----------2116-------------------------------
INT 21 - DOS 1+ - CREATE OR TRUNCATE FILE USING FCB
AH = 16h
DS:DX -> unopened FCB (see AH=0Fh), wildcards not allowed
Return: AL = status
00h successful
FFh directory full or file exists and is read-only or locked
Notes: if file already exists, it is truncated to zero length
if an extended FCB is used, the file is given the attribute in the
FCB
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=10h,AH=3Ch
----------2117-------------------------------
INT 21 - DOS 1+ - RENAME FILE USING FCB
AH = 17h
DS:DX -> modified FCB (see also AH=0Fh)
the old filename ('?' wildcards OK) is in the standard location
while the new filename ('?' wildcards OK) is stored in the 11
bytes beginning at offset 11h
Return: AL = status
00h successfully renamed
FFh no matching files,file is read-only, or new name already exists
Note: subdirectories may be renamed using an extended FCB with the
appropriate attribute
SeeAlso: AH=0Fh,AH=13h,AH=56h,INT 2F/AX=1111h
----------2118-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 18h
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get bit map of logged drives",
which is meaningless under MSDOS
SeeAlso: AH=1Dh,AH=1Eh,AH=20h,AX=4459h
----------2119-------------------------------
INT 21 - DOS 1+ - GET CURRENT DEFAULT DRIVE
AH = 19h
Return: AL = drive (00h = A:, 01h = B:, etc)
SeeAlo: AH=0Eh,AH=47h
----------211A-------------------------------
INT 21 - DOS 1+ - SET DISK TRANSFER AREA ADDRESS
AH = 1Ah
DS:DX -> Disk Transfer Area (DTA)
Notes: the DTA is set to PSP:0080h when a program is started
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=11h,AH=12h,AH=2Fh,AH=4Eh,AH=4Fh
----------211B-------------------------------
INT 21 - DOS 1+ - GET ALLOCATION INFORMATION FOR DEFAULT DRIVE
AH = 1Bh
Return: AL = sectors per cluster (allocation unit)
CX = bytes per sector
DX = total number of clusters
DS:BX -> media ID byte (see below)
Note: under DOS 1.x, DS:BX points at an actual copy of the FAT; later
versions return a pointer to a copy of the FAT's ID byte
SeeAlso: AH=1Ch,AH=36h
Values for media ID byte:
FFh floppy, double-sided, 8 sectors per track (320K)
FEh floppy, single-sided, 8 sectors per track (160K)
FDh floppy, double-sided, 9 sectors per track (360K)
FCh floppy, single-sided, 9 sectors per track (180K)
F9h floppy, double-sided, 15 sectors per track (1.2M)
F8h hard disk
F0h other
----------211C-------------------------------
INT 21 - DOS 1+ - GET ALLOCATION INFORMATION FOR SPECIFIC DRIVE
AH = 1Ch
DL = drive (00h = default, 01h = A:, etc)
Return: AL = sectors per cluster (allocation unit)
CX = bytes per sector
DX = total number of clusters
DS:BX -> media ID byte (see AH=1Bh)
Note: under DOS 1.x, DS:BX points at an actual copy of the FAT; later
versions return a pointer to a copy of the FAT's ID byte
SeeAlso: AH=1Bh,AH=36h
----------211D-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 1Dh
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get bit map of read-only
drives", which is meaningless under MSDOS
SeeAlso: AH=18h,AH=1Eh,AH=20h,AX=4459h
----------211E-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 1Eh
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "set file attributes" which was
meaningless under MSDOS 1.x
SeeAlso: AH=18h,AH=1Dh,AH=20h
----------211F-------------------------------
INT 21 - DOS 1+ - GET DRIVE PARAMETER BLOCK FOR DEFAULT DRIVE
AH = 1Fh
Return: AL = status
00h successful
DS:BX -> Drive Parameter Block (DPB) (see below for DOS 1.x,
AH=32h for DOS 2+)
FFh invalid drive
Note: this call was undocumented prior to the release of DOS 5.0; however,
only the DOS 4+ version of the DPB has been documented
SeeAlso: AH=32h
Format of DOS 1.1 and MSDOS 1.25 drive parameter block:
Offset Size Description
00h BYTE sequential device ID
01h BYTE logical drive number (0=A:)
02h WORD bytes per sector
04h BYTE highest sector number within a cluster
05h BYTE shift count to convert clusters into sectors
06h WORD starting sector number of first FAT
08h BYTE number of copies of FAT
09h WORD number of directory entries
0Bh WORD number of first data sector
0Dh WORD highest cluster number (number of data clusters + 1)
0Fh BYTE sectors per FAT
10h WORD starting sector of directory
12h WORD address of allocation table
Note: the DOS 1.0 table is the same except that the first and last fields
are missing; see INT 21/AH=32h for the DOS 2+ version
----------2120-------------------------------
INT 21 - DOS 1+ - NULL FUNCTION FOR CP/M COMPATIBILITY
AH = 20h
Return: AL = 00h
Note: corresponds to the CP/M BDOS function "get/set default user
(sublibrary) number", which is meaningless under MSDOS
SeeAlso: AH=18h,AH=1Dh,AH=1Eh,AX=4459h
----------2121-------------------------------
INT 21 - DOS 1+ - READ RANDOM RECORD FROM FCB FILE
AH = 21h
DS:DX -> opened FCB (see AH=0Fh)
Return: AL = status
00h successful
01h end of file, no data read
02h segment wrap in DTA, no data read
03h end of file, partial record read
[DTA] = record read from file
Notes: the record is read from the current file position as specified by the
random record and record size fields of the FCB
the file position is not updated after reading the record
if a partial record is read, it is zero-padded to the full size
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=14h,AH=22h,AH=27h,AH=3Fh
----------2122-------------------------------
INT 21 - DOS 1+ - WRITE RANDOM RECORD TO FCB FILE
AH = 22h
DS:DX -> opened FCB (see AH=0Fh)
[DTA] = record to write
Return: AL = status
00h successful
01h disk full
02h segment wrap in DTA
Notes: the record is written to the current file position as specified by the
random record and record size fields of the FCB
the file position is not updated after writing the record
if the record is located beyond the end of the file, the file is
extended but the intervening data remains uninitialized
if the record only partially fills a disk sector, it is copied to a
DOS disk buffer to be written out to disk at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=15h,AH=21h,AH=28h,AH=40h
----------2123-------------------------------
INT 21 - DOS 1+ - GET FILE SIZE FOR FCB
AH = 23h
DS:DX -> unopened FCB (see AH=0Fh), wildcards not allowed
Return: AL = status
00h successful (matching file found)
FCB random record field filled with size in records, rounded up
to next full record
FFh failed (no matching file found)
Note: not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=42h
----------2124-------------------------------
INT 21 - DOS 1+ - SET RANDOM RECORD NUMBER FOR FCB
AH = 24h
DS:DX -> opened FCB (see AH=0Fh)
Notes: computes the random record number corresponding to the current record
number and record size, then stores the result in the FCB
normally used when switching from sequential to random access
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=21h,AH=27h,AH=42h
----------2125-------------------------------
INT 21 - DOS 1+ - SET INTERRUPT VECTOR
AH = 25h
AL = interrupt number
DS:DX -> new interrupt handler
Notes: this function is preferred over direct modification of the interrupt
vector table
some DOS extenders place an API on this function, as it is not
directly meaningful in protected mode
SeeAlso: AX=2501h,AH=35h
----------212501-----------------------------
INT 21 P - Phar Lap 386/DOS-Extender - RESET DOS EXTENDER DATA STRUCTURES
AX = 2501h
SS = application's original SS or DS (FlashTek X-32VM)
Return: CF clear if successful
CF set on error
caller is operating on X-32 stack (FlashTek X-32VM)
Notes: Phar Lap uses INT 21/AH=25h as the entry point for all 386/DOS-Extender
system calls. Only available when directly using 386/DOS-Extender or
a compatible DOS extender, or when using a product that was created
using 386-DOS/Extender or a compatible
this function is also supported by FlashTek X-32VM
SeeAlso: AH=30h"Phar Lap"
----------212502-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET PROTECTED-MODE INTERRUPT VECTOR
AX = 2502h
CL = interrupt number
Return: CF clear
ES:EBX = CS:EIP of protected-mode interrupt handler
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2504h,INT 31/AX=0204h
----------212503-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET REAL-MODE INTERRUPT VECTOR
AX = 2503h
CL = interrupt number
Return: CF clear
EBX = CS:IP of real-mode interrupt handler
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2504h,AH=35h,INT 31/AX=0200h
----------212504-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET PROTECTED-MODE INTERRUPT VECTOR
AX = 2504h
CL = interrupt number
DS:EDX = CS:EIP of protected-mode interrupt handler
Return: CF clear
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2505h,INT 31/AX=0205h
----------212505-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET REAL-MODE INTERRUPT VECTOR
AX = 2505h
CL = interrupt number
EBX = CS:IP of real-mode interrupt handler
Return: CF clear
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2504h,INT 31/AX=0201h
----------212506-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET INT TO ALWAYS GAIN CONTRL IN PROT MODE
AX = 2506h
CL = interrupt number
DS:EDX = CS:EIP of protected-mode interrupt handler
Return: CF clear
Notes: this function modifies both the real-mode low-memory interrupt
vector table and the protected-mode Interrupt Descriptor Table (IDT)
interrupts occurring in real mode are resignaled in protected mode
this function is also supported by FlashTek X-32VM
----------212507-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SET REAL- & PROTECTED-MODE INT VECTORS
AX = 2507h
CL = interrupt numbern
DS:EDX = CS:EIP of protected-mode interrupt handler
EBX = CS:IP of real-mode interrupt handler
Return: CF clear
Notes: interrupts are disabled until both vectors have been modified
this function is also supported by FlashTek X-32VM
SeeAlso: AX=2504h,AX=2505h
----------212508-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET SEGMENT LINEAR BASE ADDRESS
AX = 2508h
BX = segment selector
Return: CF clear if successful
ECX = linear base address of segment
CF set if invalid segment selector
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2509h
----------212509-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CONVERT LINEAR TO PHYSICAL ADDRESS
AX = 2509h
EBX = linear address to convert
Return: CF clear if successful
ECX = physical address (carry flag clear)
CF set if linear address not mapped in page tables
SeeAlso: AX=2508h
----------212509-----------------------------
INT 21 - FlashTek X-32VM - GET SYSTEM SEGMENTS AND SELECTORS
AX = 2509h
Return: CF clear
EAX high word = default DS
AX = alias for 16-bit data segment
BX = real mode code segment
EDX high word = selector covering full 4GB address space
DX = default SS
ESI high word = PSP selector
SI = environment selector
----------21250A-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - MAP PHYSICAL MEMORY AT END OF SEGMENT
AX = 250Ah
ES = segment selector in the Local Descriptor Table (LDT) of segment
to modify
EBX = physical base address of memory to map (multiple of 4K)
ECX = number of physical 4K pages to map
Return: CF clear if successful
EAX = 32-bit offset in segment of mapped memory
CF set on error
EAX = error code
08h insufficient memory to create page tables
09h invalid segment selector
SeeAlso: INT 31/AX=0800h
----------21250C-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET HARDWARE INTERRUPT VECTORS
AX = 250Ch
Return: CF clear
AL = base interrupt vector for IRQ0-IRQ7
AH = base interrupt vector for IRQ8-IRQ15
BL = interrupt vector for BIOS print screen function (Phar Lap only)
Note: this function is also supported by FlashTek X-32VM
SeeAlso: INT 31/AX=0400h,INT 67/AX=DE0Ah
----------21250D-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET REAL-MODE LINK INFORMATION
AX = 250Dh
Return: CF clear
EAX = CS:IP of real-mode callback procedure that will call through
from real mode to a protected-mode routine
EBX = 32-bit real-mode address of intermode call data buffer
ECX = size in bytes of intermode call data buffer
ES:EDX = protected-mode address of intermode call data buffer
Notes: this function is also supported by FlashTek X-32VM
X-32VM guarantees the intermode buffer to be at least 4 KB
SeeAlso: AX=250Eh
Call real-mode callback with:
STACK: DWORD offset to protected-mode code
WORD placeholder for protected-mode CS
DWORD pointer to selector structure (see below)
or 0000h:0000h for defaults
var parameters for protected-mode procedure
Return: via FAR return
Format of selector structure:
Offset Size Description
00h WORD protected-mode GS selector
02h WORD protected-mode FS selector
04h WORD protected-mode ES selector
06h WORD protected-mode DS selector
----------21250E-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE
AX = 250Eh
EBX = CS:IP of real-mode procedure to call
ECX = number of two-byte words to copy from protected-mode stack
to real-mode stack
Return: CF clear if successful
all segment registers unchanged
all general registers contain values set by real-mode procedure
all other flags set as they were left by real-mode procedure
stack unchanged
CF set on error
EAX = error code
01h not enough real-mode stack space
Note: this function is also supported by FlashTek X-32VM; under X-32VM, the
call will fail if ECX > 0000003Fh
SeeAlso: AX=250Dh,AX=2510h,AH=E1h"OS/286",INT 31/AX=0301h
----------21250F-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CONVERT PROTECTED-MODE ADDRESS TO MS-DOS
AX = 250Fh
ES:EBX = 48-bit protected-mode address to convert
Return: CF clear if successful (address < 1MB)
ECX = 32-bit real-mode MS-DOS address
CF set on error (address >= 1MB)
ECX = linear address
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2510h
----------212510-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CALL REAL-MODE PROCEDURE, REGISTERS
AX = 2510h
EBX = CS:IP of real-mode procedure to call
ECX = number of two-byte words to copy to protected-mode stack to
real-mode stack
DS:EDX -> pointer to parameter block (see below)
Return: CF clear if successful
all segment registers unchanged,
EDX unchanged
all other general registers contain values set by real-mode proc
all other flags are set as they were left by real-mode procedure
real-mode register values are returned in the parameter block
CF set on error
EAX = error code
01h not enough real-mode stack space
Note: unlike most of the preceding 25xxh functions, this one is not
supported by FlashTek X-32VM
SeeAlso: AX=250Eh,AX=250Fh
Format of parameter block:
Offset Size Description
00h WORD real-mode DS value
02h WORD real-mode ES value
04h WORD real-mode FS value
06h WORD real-mode GS value
08h DWORD real-mode EAX value
0Ch DWORD real-mode EBX value
10h DWORD real-mode ECX value
14h DWORD real-mode EDX value
----------212511-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - ISSUE REAL-MODE INTERRUPT
AX = 2511h
DS:EDX -> parameter block (see below)
Return: all segment registers unchanged
EDX unchanged
all other registers contain values set by the real-mode int handler
the flags are set as they were left by the real-mode interrupt handler
real-mode register values are returned in the parameter block
Note: this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2505h,AX=250Eh,AH=E3h"OS/286",INT 31/AX=0300h
Format of parameter block:
Offset Size Description
00h WORD interrupt number
02h WORD real-mode DS value
04h WORD real-mode ES value
06h WORD real-mode FS value
08h WORD real-mode GS value
0Ah DWORD real-mode EAX value
0Eh DWORD real-mode EDX value
Note: all other real-mode values set from protected-mode registers
----------212512-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - LOAD PROGRAM FOR DEBUGGING
AX = 2512h
DS:EDX -> pointer to ASCIIZ program name
ES:EBX -> pointer to parameter block (see below)
ECX = size in bytes of LDT buffer
Return: CF clear if successful
EAX = number of segment descriptors in LDT
CF set on error
EAX = error code
02h file not found or path invalid
05h access denied
08h insufficient memory
0Ah environment invalid
0Bh invalid file format
80h LDT too small
Format of parameter block:
Offset Size Description
Input:
00h DWORD 32-bit offset of environment string
04h WORD segment of environment string
06h DWORD 32-bit offset of command-tail string
0Ah WORD segment of command-tail string
0Ch DWORD 32-bit offset of LDT buffer (size in ECX)
10h WORD segment of LDT buffer
Output:
12h WORD real-mode paragraph address of PSP (see also AH=26h)
14h WORD real/protected mode flag
0000h real mode
0001h protected mode
16h DWORD initial EIP value
1Ah WORD initial CS value
1Ch DWORD initial ESP value
20h WORD initial SS value
22h WORD initial DS value
24h WORD initial ES value
26h WORD initial FS value
28h WORD initial GS value
----------212513-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - ALIAS SEGMENT DESCRIPTOR
AX = 2513h
BX = segment selector of descriptor in GDT or LDT
CL = access-rights byte for alias descriptor
CH = use-type bit (USE16 or USE32) for alias descriptor
Return: CF clear if successful
AX = segment selector for created alias
CF set on error
EAX = error code
08h insufficient memory (can't grow LDT)
09h invalid segment selector in BX
----------212514-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - CHANGE SEGMENT ATTRIBUTES
AX = 2514h
BX = segment selector of descriptor in GDT or LDT
CL = new access-rights byte
CH = new use-type bit (USE16 or USE32)
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid selector in BX
SeeAlso: AX=2515h,INT 31/AX=0009h
----------212515-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET SEGMENT ATTRIBUTES
AX = 2515h
BX = segment selector of descriptor in GDT or LDT
Return: CF clear if successful
CL = access-rights byte for segment
CH = use-type bit (USE16 or USE32)
ECX<16-31> destroyed
CF set on error
EAX = error code
09h invalid segment selector in BX
SeeAlso: AX=2514h
----------212516-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - FREE ALL MEMORY OWNED BY LDT
AX = 2516h
???
Return: ???
----------212517-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET INFO ON DOS DATA BUFFER
AX = 2517h
???
Return: ???
----------212518-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - SPECIFY HANDLER FOR MOVED SEGMENTS
AX = 2518h
???
Return: ???
----------212519-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - GET ADDITIONAL MEMORY ERROR INFO
AX = 2519h
Return: CF clear
EAX = error code
0000h no error
0001h out of physical memory
0002h out of swap space (unable to grow swap file)
0003h out of LDT entries and unable to grow LDT
0004h unable to change extended memory allocation mark
FFFFFFFFh paging disabled
Note: VMM is the Virtual Memory Manager option
----------21251A-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - LOCK PAGES IN MEMORY
AX = 251Ah
EDX = number of 4k pages to lock
if BL = 00h
ECX = linear address of first page to lock
if BL = 01h
ES:ECX -> pointer to first page to lock
Return: CF clear if successful
CF set on error
EAX = error code
08h insufficient memory
09h invalid address range
SeeAlso: AX=251Bh,AX=EB06h,INT 31/AX=0600h
----------21251B-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - UNLOCK PAGES
AX = 251Bh
EDX = number of pages to unlock
if BL = 00h
ECX = linear address of first page to unlock
if BL = 01h
ES:ECX -> pointer to first page to unlock
Return: CF clear if successful
CF set on error
EAX = error code
09h invalid address range
SeeAlso: AX=251Ah,AX=EB07h,INT 31/AX=0601h
----------21251D-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - READ PAGE-TABLE ENTRY
AX = 251Dh
???
Return: ???
SeeAlso: AX=251Eh,AX=EB00h,INT 31/AX=0506h
----------21251E-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - WRITE PAGE-TABLE ENTRY
AX = 251Eh
???
Return: ???
SeeAlso: AX=251Dh,INT 31/AX=0507h
----------21251F-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - EXHANGE TWO PAGE-TABLE ENTRIES
AX = 251Fh
???
Return: ???
SeeAlso: AX=251Dh,AX=251Eh
----------212520-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - GET MEMORY STATISTICS
AX = 2520h
DS:EDX -> pointer to buffer at least 100 bytes in size (see below)
BL = 0 (don't reset VM stats), 1 (reset VM stats)
Return: carry flag clear
Format of VM stats buffer:
Offset Size Description
00h DWORD VM status
0001h VM subsystem is present
0000h VM not present
04h DWORD "nconvpg" number of conventional memory pages available
08h DWORD "nbimpg" number of Compaq built-in memory pages available
0Ch DWORD "nextpg" total number of extended memory pages
10h DWORD "extlim" extender memory pages limit
14h DWORD "aphyspg" number of physical memory pages allocated to appl
18h DWORD "alockpg" number of locked pages owned by application
1Ch DWORD "sysphyspg" number physical memory pages allocated to system
20h DWORD "nfreepg" number of free physical pages; approx if EMS VCPI
24h DWORD linear address of beginning of application address space
28h DWORD linear address of end of application address space
2Ch DWORD number of seconds since last time VM stats were reset
30h DWORD number of page faults since last time
34h DWORD number of pages written to swap file since last time
38h DWORD number of reclaimed pages (page faults on swapped pages)
3Ch DWORD number of virtual pages allocated to the application
40h DWORD size in pages of swap file
44h DWORD number of system pages allocated with EMS calls
48h DWORD minimum number of conventional memory pages
4Ch DWORD maximum size in bytes to which swap file can be increased
50h DWORD "vmflags" bit 0 = 1 if page fault in progress
54h 16 BYTEs reserved for future expansion (set to zero)
----------212521-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S EXTENDED MEMORY USAGE
AX = 2521h
EBX = max 4k pages of physical extended memory which program may use
Return: CF clear if successful
EBX = maximum limit in pages
ECX = minimum limit in pages
CF set on error
EAX = error code
08h insufficient memory or -nopage switch used
SeeAlso: AX=2522h
----------212522-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - SPECIFY ALTERNATE PAGE-FAULT HANDLER
AX = 2522h
???
Return: ???
SeeAlso: AX=2523h
----------212523-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - SPECIFY OUT-OF-SWAP-SPACE HANDLER
AX = 2523h
???
Return: ???
SeeAlso: AX=2522h
----------212524-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - INSTALL PAGE-REPLACEMENT HANDLERS
AX = 2524h
???
Return: ???
----------212525-----------------------------
INT 21 - Phar Lap 386/DOS-Extender VMM - LIMIT PROGRAM'S CONVENTIONAL MEM USAGE
AX = 2525h
EBX = limit in 4k pages of physical conventional memory which program
may use
Return: CF clear if successful
EBX = maximum limit in pages
ECX = minimum limit in pages
CF set on error
EAX = error code
08h insufficient memory or -nopage switch used
SeeAlso: AX=2521h
----------212526-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - GET CONFIGURATION INFORMATION
AX = 2526h
???
Return: ???
----------21252B-----------------------------
INT 21 - FlashTek X-32VM - VIRTUAL MEMORY MANAGEMENT - PAGE LOCKING
AX = 252Bh
BH = function
05h lock pages
06h unlock pages
BL = address type
00h linear address
ECX = linear start address of memory region
01h segmented address
ES:ECX -> start of memory region
EDX = size of memory region in bytes
Return: CF clear if successful
CF set on error
Note: if X-32 is not using virtual memory, this function always succeeds
----------212532-----------------------------
INT 21 - FlashTek X-32VM - GET EXCEPTION HANDLER VECTOR
AX = 2532h
CL = exception number (00h-0Fh)
Return: CF clear if successful
ES:EBX = CS:EIP of current exception handler
CF set on error (CL > 0Fh)
SeeAlso: AX=2533h
----------212533-----------------------------
INT 21 - FlashTek X-32VM - SET EXCEPTION HANDLER VECTOR
AX = 2533h
CL = exception number (00h-0Fh)
DS:EDX = CS:EIP of new exception handler
Return: CF clear if successful
CF set on error (CL > 0Fh)
SeeAlso: AX=2532h
----------2125C0-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - ALLOCATE MS-DOS MEMORY BLOCK
AX = 25C0h
BX = number of 16-byte paragraphs of MS-DOS memory requested
Return: CF clear if successful
AX = real-mode paragraph address of memory
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
08h insufficient memory
BX = size in paragraphs of largest available memory block
SeeAlso: AX=25C1h,AX=25C2h
----------2125C1-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - RELEASE MS-DOS MEMORY BLOCK
AX = 25C1h
CX = real-mode paragraph address of memory block to free
Return: CF clear if successful
EAX destroyed
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
09h invalid memory block address in CX
SeeAlso: AX=25C0h,AX=25C2h
----------2125C2-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - MODIFY MS-DOS MEMORY BLOCK
AX = 25C2h
BX = new requested block size in paragraphs
CX = real-mode paragraph address of memory block to modify
Return: CF clear if successful
EAX destroyed
CF set on error
AX = error code
07h MS-DOS memory control blocks destroyed
08h insufficient memory
09h invalid memory block address in CX
BX = size in paragraphs of largest available memory block
SeeAlso: AX=25C0h,AX=25C1h
----------2125C3-----------------------------
INT 21 - Phar Lap 386/DOS-Extender - EXECUTE PROGRAM
AX = 25C3h
ES:EBX -> pointer to parameter block (see below)
DS:EDX -> pointer to ASCIIZ program filename
Return: CF clear if successful
all registers unchanged
CF set on error
EAX = error code
01h function code in AL is invalid ???
02h file not found or path invalid
05h access denied
08h insufficient memory to load program
0Ah environment invalid
0Bh invalid file format
Format of parameter block:
Offset Size Description
00h DWORD 32-bit offset of environment string
04h WORD segment selector of environment string
06h DWORD 32-bit offset of command-tail string
0Ah WORD segment selector of command-tail string
----------2126-------------------------------
INT 21 - DOS 1+ - CREATE NEW PROGRAM SEGMENT PREFIX
AH = 26h
DX = segment at which to create PSP (see below)
Notes: new PSP is updated with memory size information; INTs 22h, 23h, 24h
taken from interrupt vector table
(DOS 2+) DOS assumes that the caller's CS is the segment of the PSP to
copy
SeeAlso: AH=4Bh,AH=50h,AH=51h,AH=55h,AH=62h,AH=67h
Format of PSP:
Offset Size Description
00h 2 BYTEs INT 20 instruction for CP/M CALL 0 program termination
the CDh 20h here is often used as a signature for a valid PSP
02h WORD segment of first byte beyond memory allocated to program
04h BYTE unused filler
05h BYTE CP/M CALL 5 service request (FAR JMP to 000C0h)
BUG: (DOS 2+) PSPs created by INT 21/AH=4Bh point at 000BEh
06h WORD CP/M compatibility--size of first segment for .COM files
08h 2 BYTEs remainder of FAR JMP at 05h
0Ah DWORD stored INT 22 termination address
0Eh DWORD stored INT 23 control-Break handler address
12h DWORD DOS 1.1+ stored INT 24 critical error handler address
16h WORD segment of parent PSP
18h 20 BYTEs DOS 2+ Job File Table, one byte per file handle, FFh = closed
2Ch WORD DOS 2+ segment of environment for process
2Eh DWORD DOS 2+ process's SS:SP on entry to last INT 21 call
32h WORD DOS 3+ number of entries in JFT (default 20)
34h DWORD DOS 3+ pointer to JFT (default PSP:0018h)
38h DWORD DOS 3+ pointer to previous PSP (default FFFFFFFFh in 3.x)
used by SHARE in DOS 3.3
3Ch 4 BYTEs unused by DOS versions <= 5.00
reportedly used by Novell NetWare shell 3.x
40h 2 BYTEs DOS 5.0 version to return on INT 21/AH=30h
42h 6 BYTEs unused by DOS versions <= 5.00
48h BYTE (MSWindows3) bit 0 set if non-Windows application (WINOLDAP)
49h 7 BYTEs unused by DOS versions <= 5.00
50h 3 BYTEs DOS 2+ service request (INT 21/RETF instructions)
53h 9 BYTEs unused in DOS versions <= 5.00
5Ch 16 BYTEs first default FCB, filled in from first commandline argument
overwrites second FCB if opened
6Ch 16 BYTEs second default FCB, filled in from second commandline argument
overwrites beginning of commandline if opened
7Ch 4 BYTEs unused
80h 128 BYTEs commandline / default DTA
command tail is BYTE for length of tail, N BYTEs for the tail,
followed by a BYTE containing 0Dh
Notes: in DOS versions 3.0 and up, the limit on simultaneously open files may
be increased by allocating memory for a new open file table, filling
it with FFh, copying the first 20 bytes from the default table, and
adjusting the pointer and count at 34h and 32h. However, DOS
versions through at least 3.30 will only copy the first 20 file
handles into a child PSP (including the one created on EXEC).
network redirectors based on the original MS-Net implementation use
values of 80h-FEh in the open file table to indicate remote files;
Novell NetWare reportedly also uses values of 80h-FEh
MSDOS 5.00 incorrectly fills the FCB fields when loading a program
high; the first FCB is empty and the second contains the first
parameter
some DOS extenders place protected-mode values in various PSP fields
such as the "parent" field, which can confuse PSP walkers. Always
check either for the CDh 20h signature or that the suspected PSP is
at the beginning of a memory block which owns itself (the preceding
paragraph should be a valid MCB with "owner" the same as the
suspected PSP).
Format of environment block:
Offset Size Description
00h N BYTEs first environment variable, ASCIZ string of form "var=value"
N BYTEs second environment variable, ASCIZ string
...
N BYTEs last environment variable, ASCIZ string of form "var=value"
BYTE 00h
---DOS 3+---
WORD number of strings following environment (normally 1)
N BYTEs ASCIZ full pathname of program owning this environment
other strings may follow
----------2127-------------------------------
INT 21 - DOS 1+ - RANDOM BLOCK READ FROM FCB FILE
AH = 27h
CX = number of records to read
DS:DX -> opened FCB (see AH=0Fh)
Return: AL = status
00h successful, all records read
01h end of file, no data read
02h segment wrap in DTA, no data read
03h end of file, partial read
[DTA] = records read from file
CX = number of records read (return AL = 00h or 03h)
Notes: read begins at current file position as specified in FCB; the file
position is updated after reading
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=21h,AH=28h,AH=3Fh
----------2128-------------------------------
INT 21 - DOS 1+ - RANDOM BLOCK WRITE TO FCB FILE
AH = 28h
CX = number of records to write
DS:DX -> opened FCB (see AH=0Fh)
[DTA] = records to write
Return: AL = status
00h successful
01h disk full or file read-only
02h segment wrap in DTA
CX = number of records written
Notes: write begins at current file position as specified in FCB; the file
position is updated after writing
if CX = 0000h on entry, no data is written; instead the file size is
adjusted to be the same as the file position specified by the random
record and record size fields of the FCB
if the data to be written is less than a disk sector, it is copied into
a DOS disk buffer, to be written out to disk at a later time
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=22h,AH=27h,AH=40h,AH=59h
----------2129-------------------------------
INT 21 - DOS 1+ - PARSE FILENAME INTO FCB
AH = 29h
AL = parsing options
bit 0: skip leading separators
bit 1: use existing drive number in FCB if no drive is specified,
instead of setting field to zero
bit 2: use existing filename in FCB if no base name is specified,
instead of filling field with blanks
bit 3: use existing extension in FCB if no extension is specified,
instead of filling field with blanks
bits 4-7: reserved (0)
DS:SI -> filename string (both '*' and '?' wildcards OK)
ES:DI -> buffer for unopened FCB
Return: AL = result code
00h successful parse, no wildcards encountered
01h successful parse, wildcards present
FFh failed (invalid drive specifier)
DS:SI -> first unparsed character
ES:DI buffer filled with unopened FCB (see AH=0Fh)
Notes: asterisks expanded to question marks in the FCB
all processing stops when a filename terminator is encountered
cannot be used with filespecs which include a path (DOS 2+)
SeeAlso: AH=0Fh,AH=16h,AH=26h
----------212A-------------------------------
INT 21 - DOS 1+ - GET SYSTEM DATE
AH = 2Ah
Return: CX = year (1980-2099)
DH = month
DL = day
---DOS 1.10+---
AL = day of week (00h=Sunday)
SeeAlso: AH=2Bh"DOS",AH=2Ch,AH=E7h,INT 1A/AH=04h,INT 2F/AX=120Dh
----------212B-------------------------------
INT 21 - DOS 1+ - SET SYSTEM DATE
AH = 2Bh
CX = year (1980-2099)
DH = month
DL = day
Return: AL = status
00h successful
FFh invalid date, system date unchanged
Note: DOS 3.3+ also sets CMOS clock
SeeAlso: AH=2Ah,AH=2Dh,INT 1A/AH=05h
----------212B--CX4149-----------------------
INT 21 - AI Architects - ??? - INSTALLATION CHECK
AH = 2Bh
CX = 4149h ('AI')
DX = 413Fh ('A?')
Return: AL <> FFh if installed
Note: Borland's TKERNEL makes this call
----------212B--CX4358-----------------------
INT 21 - PC Tools v5.x PC-Cache - INSTALLATION CHECK
AH = 2Bh
CX = 4358h ('CX')
Return: AL = FFh if PC-Cache not installed
AL = 00h if installed
CX = 6378h ('cx')
BX = ???
DX = ???
SeeAlso: INT 16/AX=FFA5h/CX=1111h
----------212B--CX4445-----------------------
INT 21 - DESQview - INSTALLATION CHECK
AH = 2Bh
CX = 4445h ('DE')
DX = 5351h ('SQ')
AL = subfunction (DV v2.00+)
01h get version
Return: BX = version (BH = major, BL = minor)
Note: early copies of v2.00 return 0002h
02h get shadow buffer info, and start shadowing
Return: BH = rows in shadow buffer
BL = columns in shadow buffer
DX = segment of shadow buffer
04h get shadow buffer info
Return: BH = rows in shadow buffer
BL = columns in shadow buffer
DX = segment of shadow buffer
05h stop shadowing
Return: AL = FFh if DESQview not installed
Notes: in DESQview v1.x, there were no subfunctions; this call only identified
whether or not DESQview was loaded. DESQview v2.52 performs function
01h for all subfunction requests 0Ch and higher and appears to ignore
all lower-numbered functions not listed here.
DESQview versions 2.5x are part of DESQview/X v1.0x.
BUG: subfunction 05h does not appear to work correctly in DESQview 2.52
SeeAlso: INT 10/AH=FEh,INT 10/AH=FFh,INT 15/AX=1024h,INT 15/AX=DE30h
----------212B--CX454C-----------------------
INT 21 - ELRES v1.1 - INSTALLATION CHECK
AH = 2Bh
CX = 454Ch ('EL')
DX = 5253h ('RS')
Return: ES:BX -> ELRES history structure (see below)
DX = DABEh (signature, DAve BEnnett)
Note: ELRES is an MSDOS return code (errorlevel) recorder by David H. Bennett
which stores recent errorlevel values, allows them to be retrieved
for use in batch files, and can place them in an environment variable
SeeAlso: AH=4Bh"ELRES",AH=4Dh
Format of ELRES history structure:
Offset Size Description
00h WORD number of return codes which can be stored by following buffer
02h WORD current position in buffer (treated as a ring)
04h N BYTEs ELRES buffer
----------212B01CX5441-----------------------
INT 21 - TAME v2.10+ - INSTALLATION CHECK
AX = 2B01h
CX = 5441h ('TA')
DX = 4D45h ('ME')
---v2.60---
BH = ???
00h skip ???, else do
Return: AL = 02h if installed
ES:DX -> data area in TAME-RES (see below)
Note: TAME is a shareware program by David G. Thomas which gives up CPU time
to other partitions under a multitasker when the current partition's
program incessantly polls the keyboard or system time
Format of TAME 2.10-2.20 data area:
Offset Size Description
00h BYTE data structure minor version number (01h in TAME 2.20)
01h BYTE data structure major version number (07h in TAME 2.20)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD original INT 10h
16h DWORD original INT 14h
1Ah DWORD original INT 15h
1Eh DWORD original INT 16h
22h DWORD original INT 17h
26h DWORD original INT 21h
2Ah DWORD original INT 28h
2Eh WORD offset of TAME INT 10h handler
30h WORD offset of TAME INT 14h handler
32h WORD offset of TAME INT 15h handler
34h WORD offset of TAME INT 16h handler
36h WORD offset of TAME INT 17h handler
38h WORD offset of TAME INT 21h handler
3Ah WORD offset of TAME INT 28h handler
3Ch WORD X in /max:X,Y or /freq:X,Y
3Eh WORD Y in /max:X,Y or /freq:X,Y
40h WORD number of polls remaining before next task switch
42h WORD /KEYIDLE value
44h BYTE flags for interrupts already grabbed by TAME
bit 0: INT 10h
1: INT 14h
2: INT 15h
3: INT 16h
4: INT 17h
5: INT 21h
6: INT 28h
45h BYTE flags for interrupts which may be acted on (same bits as above)
46h BYTE TAME enabled (01h) or disabled (00h)
47h BYTE /TIMEPOLL (01h) or /NOTIMEPOLL (00h)
48h BYTE /NOTIMER (01h) or /TIMER (00h)
49h BYTE window or task number for this task
4Ah BYTE multitasker type ???
01h DESQview
02h DoubleDOS
03h TopView
???
4Bh BYTE type of task switching selected
bit 0: DESQview???
1: DoubleDOS???
2: TopView???
3: KeySwitch
4: HLT instruction
4Ch BYTE ???
4Dh BYTE flags
bit 1: /FREQ instead of /MAX
4Eh BYTE /FG: value
4Fh BYTE task switches left until next FGONLY DESQview API call
50h BYTE ???
Format of TAME 2.30 data area:
Offset Size Description
00h BYTE data structure minor version number (02h in TAME 2.30)
01h BYTE data structure major version number (0Ah in TAME 2.30)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD time of last /CLEAR or TAME-RES load
16h DWORD time yielded
1Ah DWORD time spent polling
1Eh DWORD time spent waiting on key input with INT 16/AH=01h,11h
22h DWORD original INT 10h
26h DWORD original INT 14h
2Ah DWORD original INT 15h
2Eh DWORD original INT 16h
32h DWORD original INT 17h
36h DWORD original INT 21h
3Ah DWORD original INT 28h
3Eh WORD offset of TAME INT 10h handler
40h WORD offset of TAME INT 14h handler
42h WORD offset of TAME INT 15h handler
44h WORD offset of TAME INT 16h handler
46h WORD offset of TAME INT 17h handler
48h WORD offset of TAME INT 21h handler
4Ah WORD offset of TAME INT 28h handler
4Ch WORD X in /max:X,Y or /freq:X,Y
4Eh WORD Y in /max:X,Y or /freq:X,Y
50h WORD number of polls remaining before next task switch
52h WORD /KEYIDLE value
54h WORD /FG: value
56h WORD task switches left until next FGONLY DESQview API call
58h WORD multitasker version
5Ah WORD virtual screen segment
5Ch BYTE flags for interrupts already grabbed by TAME
bit 0: INT 10h
1: INT 14h
2: INT 15h
3: INT 16h
4: INT 17h
5: INT 21h
6: INT 28h
5Dh BYTE flags for interrupts which may be acted on (same bits as above)
5Eh BYTE window or task number for this task
5Fh BYTE multitasker type
01h DESQview
02h DoubleDOS
03h TopView
04h OmniView
05h VM/386
60h BYTE type of task switching selected (bit flags)
bit 0: DESQview
1: DoubleDOS
2: TopView
3: OmniView
4: KeySwitch
5: HLT instruction
61h BYTE watch_DOS
62h BYTE bit flags
bit 0: TAME enabled
1: /FREQ instead of /MAX (counts in 3Ch and 3Eh per tick)
2: /TIMEPOLL
3: /KEYPOLL
4: inhibit timer
5: enable status monitoring
63h BYTE old status
64h WORD signature DA34h
Format of TAME 2.60 data area:
Offset Size Description
00h BYTE data structure minor version number (02h in TAME 2.60)
01h BYTE data structure major version number (0Bh in TAME 2.60)
02h DWORD number of task switches
06h DWORD number of keyboard polls
0Ah DWORD number of time polls
0Eh DWORD number of times DESQview told program runs only in foreground
12h DWORD time of last /CLEAR or TAME-RES load
16h DWORD time yielded
1Ah DWORD time spent polling
1Eh DWORD time spent waiting on key input with INT 16/AH=01h,11h
22h 4 BYTEs ???
26h DWORD original INT 10h
2Ah DWORD original INT 14h
2Eh DWORD original INT 15h
32h DWORD original INT 16h
36h DWORD original INT 17h
3Ah DWORD original INT 21h
3Eh DWORD original INT 28h
42h WORD offset of TAME INT 10h handler
44h WORD offset of TAME INT 14h handler
46h WORD offset of TAME INT 15h handler
48h WORD offset of TAME INT 16h handler
4Ah WORD offset of TAME INT 17h handler
4Ch WORD offset of TAME INT 21h handler
4Eh WORD offset of TAME INT 28h handler
50h WORD X in /max:X,Y or /freq:X,Y
52h WORD Y in /max:X,Y or /freq:X,Y
54h WORD number of polls remaining before next task switch
56h WORD /KEYIDLE value
58h 4 BYTEs ???
5Ch WORD X in /boost:X,Y
5Eh WORD Y in /boost:X,Y
60h WORD /FG: value
62h WORD task switches left until next FGONLY DESQview API call
64h WORD multitasker version ???
66h WORD virtual screen segment
68h BYTE flags for interrupts already grabbed by TAME
bit 0: INT 10h
1: INT 14h
2: INT 15h
3: INT 16h
4: INT 17h
5: INT 21h
6: INT 28h
69h BYTE flags for interrupts which may be acted on (same bits as above)
6Ah BYTE window or task number for this task
6Bh BYTE multitasker type
01h DESQview
02h DoubleDOS
03h TopView
04h OmniView
05h VM/386
6Ch BYTE type of task switching selected (bit flags)
bit 0: DESQview
1: DoubleDOS
2: TopView
3: OmniView
4: KeySwitch
5: HLT instruction
6Dh BYTE watch_DOS
6Eh BYTE bit flags
bit 0: TAME enabled
1: /FREQ instead of /MAX (counts in 50h and 52h per tick)
2: /TIMEPOLL
3: /KEYPOLL
4: inhibit timer
5: enable status monitoring
6Fh BYTE old status
70h WORD signature DA34h
----------212B44BX4D41-----------------------
INT 21 - pcANYWHERE IV/LAN - INSTALLATION CHECK
AX = 2B44h ('D')
BX = 4D41h ('MA')
CX = 7063h ('pc')
DX = 4157h ('AW')
Return: AX = 4F4Bh ('OK') if large host resident
= 6F6Bh ('ok') if small host resident
CX:DX -> API entry point
SeeAlso: INT 16/AH=79h
Call API entry point with:
AX = 0000h get pcANYWHERE IV version
DS:SI -> BYTE buffer for host type code
Return: AH = version number
AL = revision number
DS:DI buffer byte filled with
00h full-featured host
01h limited-feature LAN host
other API may not be supported
AX = 0001h initialize operation
DS:SI -> initialization request structure (see below)
Return: AX = function status (see below)
AX = 0002h get status
Return: AH = current operating mode (see init req structure below)
AL = current connection status
bit 0: a physical connection is active
bit 1: remove screen updating is active
bit 2: connection checking is active
bit 3: hot key detection is active
bit 4: background file transfer is active
AX = 0003h suspend remote screen updates
Return: AX = function status (see below)
AX = 0004h resume screen updates
Return: AX = function status (see below)
AX = 0005h end current remote access session
DS:SI -> termination request structure (see below)
Return: AX = function status (see below)
AX = 0006h remove pcANYWHERE IV from memory
Return: AX = status
0000h successful
FFD2h unable to release allocated memory
FFD1h unable to release interrupt vectors
AX = 8000h read data from communications channel
DS:BX -> buffer
CX = buffer size
Return: AX >= number of characters read/available
AX < 0 on error
AX = 8001h write data to communications channel
DS:BX -> buffer
CX = buffer size
Return: AX >= number of characters written
AX < 0 on error
AX = 8002h get connection status
Return: AX = status
> 0000h if connection active
= 0000h if connection lost
< 0000h on error
Format of initialization request structure:
Offset Size Description
00h BYTE operating mode
00h wait for a call
01h hot key activates
02h incoming call activates
03h initiate a call
01h 3 BYTEs user ID to append to config file names
04h WORD DS-relative pointer to path for config files
06h WORD DS-relative pointer to path for program files
Format of termination request structure:
Offset Size Description
00h BYTE operating mode after termination
00h wait for a call
01h hot key activates
02h incoming call activates
80h use current mode
FFh remove from memory
Values for function status:
0000h function completed successfully
FFF2h unable to establish a connection when operating mode is
"Initiate a call"
FFF3h modem configuration is invalid (corrupt config)
FFF4h modem initialization failed (no modem response)
FFF5h the communications device could not be initialized
FFF6h the host operator aborted the function
FFF7h the communications driver type specified in the configuration file is
different than the one loaded when pcANYWHERE IV was initially started
FFF9h the configuration file is invalid
FFFAh the configuration file could not be found
FFFBh no session is active
FFFCh a remote access session is active
FFFDh the specified operating mode is invalid
----------212C-------------------------------
INT 21 - DOS 1+ - GET SYSTEM TIME
AH = 2Ch
Return: CH = hour
CL = minute
DH = second
DL = 1/100 seconds
Note: on most systems, the resolution of the system clock is about 5/100sec,
so returned times generally do not increment by 1
on some systems, DL may always return 00h
SeeAlso: AH=2Ah,AH=2Dh,AH=E7h,INT 1A/AH=00h,INT 1A/AH=02h,INT 1A/AH=FEh
SeeAlso: INT 2F/AX=120Dh
----------212D-------------------------------
INT 21 - DOS 1+ - SET SYSTEM TIME
AH = 2Dh
CH = hour
CL = minute
DH = second
DL = 1/100 seconds
Return: AL = result
00h successful
FFh invalid time, system time unchanged
Note: DOS 3.3+ also sets CMOS clock
SeeAlso: AH=2Bh"DOS",AH=2Ch,INT 1A/AH=01h,INT 1A/AH=03h,INT 1A/AH=FFh"AT&T"
----------212E--DL00-------------------------
INT 21 - DOS 1+ - SET VERIFY FLAG
AH = 2Eh
DL = 00h (DOS 1.x/2.x only)
AL = new state of verify flag
00h off
01h on
Notes: default state at system boot is OFF
when ON, all disk writes are verified provided the device driver
supports read-after-write verification
SeeAlso: AH=54h
----------212F-------------------------------
INT 21 - DOS 2+ - GET DISK TRANSFER AREA ADDRESS
AH = 2Fh
Return: ES:BX -> current DTA
Note: under the FlashTek X-32 DOS extender, the pointer is in ES:EBX
SeeAlso: AH=1Ah
----------2130-------------------------------
INT 21 - DOS 2+ - GET DOS VERSION
AH = 30h
---DOS 5.0---
AL = what to return in BH
00h OEM number (as for DOS 2.0-4.0x)
01h version flag
Return: AL = major version number (00h if DOS 1.x)
AH = minor version number
BL:CX = 24-bit user serial number (most versions do not use this)
---if DOS <5 or AL=00h---
BH = OEM number
00h IBM
05h Zenith
16h DEC
23h Olivetti
29h Toshiba
4Dh Hewlett-Packard
99h STARLITE architecture (OEM DOS, NETWORK DOS, SMP DOS)
FFh Microsoft, Phoenix
---if DOS 5.0 and AL=01h---
BH = version flag
08h DOS is in ROM
10h DOS is in HMA
Notes: the OS/2 v1.x Compatibility Box returns major version 0Ah (10)
the OS/2 v2.x Compatibility Box returns major version 14h (20)
the Windows/NT DOS box returns major version 1Eh (30)
DOS 4.01 and 4.02 identify themselves as version 4.00; use
INT 21/AH=87h to distinguish between the original European MSDOS 4.00
and the later PCDOS 4.0x and MSDOS 4.0x
generic MSDOS 3.30, Compaq MSDOS 3.31, and others identify themselves
as PC-DOS by returning OEM number 00h
the version returned under DOS 4.0x may be modified by entries in
the special program list (see AH=52h)
the version returned under DOS 5.0 may be modified by SETVER; use
AX=3306h to get the true version number
SeeAlso: AX=3000h/BX=3000h,AX=3306h,AX=4452h,AH=87h,INT 15/AX=4900h
SeeAlso: INT 2F/AX=122Fh,INT 2F/AX=E002h
----------2130-------------------------------
INT 21 - Phar Lap 386/DOS-Extender, Intel Code Builder - INSTALLATION CHECK
AH = 30h
EAX = 00003000h
EBX = 50484152h ("PHAR")
Return: AL = major DOS version
AH = minor DOS version
EAX bits 31-16 = 4458h ('DX') if 386/DOS-extender installed
BL = ASCII major version number
EAX bits 31-16 = 4243h ('BC') if Intel Code Builder installed
EDX = address of GDA
SeeAlso: AX=2501h,AX=FF00h,INT 2F/AX=F100h
----------2130--DXABCD-----------------------
INT 21 - VIRUS - "Possessed" - INSTALLATION CHECK
AH = 30h
DX = ABCDh
Return: DX = DCBAh if installed
SeeAlso: AX=0D20h,AX=30F1h
----------213000-----------------------------
INT 21 - Btrieve Multi-User - INSTALLATION CHECK
AX = 3000h
Return: AL >= 03h if INT 2F handler installed
SeeAlso: INT 2F/AX=AB00h,INT 7B"Btrieve",INT 7F/AX=0200h
----------213000BX1234-----------------------
INT 21 - CTask 2.0+ - INSTALLATION CHECK
AX = 3000h
BX = 1234h
DS:DX -> 8-byte version string (DX < FFF0h) "CTask21",00h for v2.1-2.2
Return: AL = DOS major version
AH = DOS minor version
CX:BX -> Ctask global data block
Notes: if first eight bytes of returned data block equal eight bytes passed
in, CTask is resident
CTask is a multitasking kernel for C written by Thomas Wagner
----------213000BX3000-----------------------
INT 21 - PC-MOS/386 v3.0 - INSTALLATION CHECK/GET VERSION
AX = 3000h
BX = 3000h
CX = DX = 3000h
Return: AX = PC-MOS version
Program: PC-MOS/386 is a multitasking/multiuser MSDOS-compatible operating
system by Software Links, Inc.
SeeAlso: AH=30h,INT 38/AH=02h,INT 38/AH=10h
----------2130F1-----------------------------
INT 21 - VIRUS - "Dutch-555"/"Quit 1992" - INSTALLATION CHECK
AX = 30F1h
Return: AL = 00h if resident
SeeAlso: AH=30h/DX=ABCDh,AX=330Fh
----------2131-------------------------------
INT 21 - DOS 2+ - TERMINATE AND STAY RESIDENT
AH = 31h
AL = return code
DX = number of paragraphs to keep resident
Return: never
Notes: the value in DX only affects the memory block containing the PSP;
additional memory allocated via AH=48h is not affected
the minimum number of paragraphs which will remain resident is 11h
for DOS 2.x and 06h for DOS 3+
most TSRs can save some memory by releasing their environment block
before terminating (see AH=26h,AH=49h)
SeeAlso: AH=00h,AH=4Ch,AH=4Dh,INT 20,INT 22,INT 27
----------2132-------------------------------
INT 21 - DOS 2+ - GET DOS DRIVE PARAMETER BLOCK FOR SPECIFIC DRIVE
AH = 32h
DL = drive number (00h = default, 01h = A:, etc)
Return: AL = status
00h successful
DS:BX -> Drive Parameter Block (DPB) for specified drive
FFh invalid or network drive
Notes: the OS/2 compatibility box supports the DOS 3.3 version of this call
except for the DWORD at offset 12h
this call updates the DPB by reading the disk; the DPB may be accessed
via the DOS list of lists (see AH=52h) if disk access is not
desirable.
undocumented prior to the release of DOS 5.0; only the DOS 4+ version
of the DPB has been documented, however
SeeAlso: AH=1Fh,AH=52h
Format of DOS Drive Parameter Block:
Offset Size Description
00h BYTE drive number (00h = A:, 01h = B:, etc)
01h BYTE unit number within device driver
02h WORD bytes per sector
04h BYTE highest sector number within a cluster
05h BYTE shift count to convert clusters into sectors
06h WORD number of reserved sectors at beginning of drive
08h BYTE number of FATs
09h WORD number of root directory entries
0Bh WORD number of first sector containing user data
0Dh WORD highest cluster number (number of data clusters + 1)
16-bit FAT if greater than 0FF6h, else 12-bit FAT
0Fh BYTE number of sectors per FAT
10h WORD sector number of first directory sector
12h DWORD address of device driver header
16h BYTE media ID byte
17h BYTE 00h if disk accessed, FFh if not
18h DWORD pointer to next DPB
---DOS 2.x---
1Ch WORD cluster containing start of current directory, 0000h=root,
FFFFh = unknown
1Eh 64 BYTEs ASCIZ pathname of current directory for drive
---DOS 3.x---
1Ch WORD cluster at which to start search for free space when writing
1Eh WORD number of free clusters on drive, FFFFh = unknown
---DOS 4.0-5.0---
0Fh WORD number of sectors per FAT
11h WORD sector number of first directory sector
13h DWORD address of device driver header
17h BYTE media ID byte
18h BYTE 00h if disk accessed, FFh if not
19h DWORD pointer to next DPB
1Dh WORD cluster at which to start search for free space when writing,
usually the last cluster allocated
1Fh WORD number of free clusters on drive, FFFFh = unknown
----------2133-------------------------------
INT 21 - DOS 2+ - EXTENDED BREAK CHECKING
AH = 33h
AL = subfunction
00h get current extended break state
Return: DL = current state, 00h = off, 01h = on
01h set state of extended ^C/^Break checking
DL = 00h off, check only on character I/O functions
01h on, check on all DOS functions
Note: under DOS 3.1+, this function does not use any of the DOS-internal and
may thus be called at any time
SeeAlso: AX=3302h
----------213302-----------------------------
INT 21 - DOS 3.x+ internal - GET AND SET EXTENDED CONTROL-BREAK CHECKING STATE
AX = 3302h
DL = new state
00h for OFF or 01h for ON
Return: DL = old state of extended BREAK checking
Note: this function does not use any of the DOS-internal stacks and may thus
be called at any time; one possible use is modifying Control-Break
checking from within an interrupt handler or TSR
SeeAlso: AH=33h
----------213305-----------------------------
INT 21 - DOS 4+ - GET BOOT DRIVE
AX = 3305h
Return: DL = boot drive (1=A:,...)
Notes: fully reentrant
NEC 9800-series PCs always call the boot drive A: and assign the other
drive letters sequentially to the other drives in the system
----------213306-----------------------------
INT 21 - DOS 5.0 - GET TRUE VERSION NUMBER
AX = 3306h
Return: BL = major version
BH = minor version
DL = revision (bits 2-0, all others 0)
DH = version flags
bit 3: DOS is in ROM
bit 4: DOS in in HMA
Notes: this function always returns the true version number, unlike AH=30h,
whose return value may be changed with SETVER
because of the conflict from the CBIS PowerLAN redirector (see next
entry), programs should check whether BH is less than 100 (64h)
and BL is at least 5 before accepting the returned BX as the true
version number; however, even this is not entirely reliable when
that redirector is loaded
fully reentrant
BUG: DR-DOS 5.0 and 6.0 return CF set/AX=0001h for INT 21/AH=33h
subfunctions other than 00h-02h and 05h, while MS-DOS returns AL=FFh
for invalid subfunctions
SeeAlso: AH=30h,INT 2F/AX=112Fh
----------213306-----------------------------
INT 21 - CBIS POWERLAN - NETWORK REDIRECTOR - ???
AX = 3306h
Return: AX = 3306h
BL = ??? (usually 00h)
BH = ??? (usually 00h or FFh)
Note: unknown function, is in conflict with DOS 5.0 version call
SeeAlso: AX=3306h"DOS"
----------21330F-----------------------------
INT 21 - VIRUS - "Burghofer" - INSTALLATION CHECK
AX = 330Fh
Return: AL = 0Fh if resident (DOS returns AL=FFh)
SeeAlso: AX=30F1h,AX=33E0h
----------2133E0-----------------------------
INT 21 - VIRUS - "Oropax" - INSTALLATION CHECK
AX = 33E0h
Return: AL = E0h if resident (DOS returns AL=FFh)
SeeAlso: AX=330Fh,AX=357Fh
----------2134-------------------------------
INT 21 - DOS 2+ - GET ADDRESS OF INDOS FLAG
AH = 34h
Return: ES:BX -> one-byte InDOS flag
Notes: the value of InDOS is incremented whenever an INT 21 function begins
and decremented whenever one completes
during an INT 28 call, it is safe to call some INT 21 functions even
though InDOS may be 01h instead of zero
InDOS alone is not sufficient for determining when it is safe to
enter DOS, as the critical error handling decrements InDOS and
increments the critical error flag for the duration of the critical
error. Thus, it is possible for InDOS to be zero even if DOS is
busy.
the critical error flag is the byte immediately following InDOS in
DOS 2.x, and the byte BEFORE the InDOS flag in DOS 3+ (except COMPAQ
DOS 3.0, where the critical error flag is located 1AAh bytes BEFORE
the critical section flag)
For DOS 3.1+, an undocumented call exists to get the address of the
critical error flag (see AX=5D06h)
this function was undocumented prior to the release of DOS 5.0.
SeeAlso: AX=5D06h,AX=5D0Bh,INT 28
----------2135-------------------------------
INT 21 - DOS 2+ - GET INTERRUPT VECTOR
AH = 35h
AL = interrupt number
Return: ES:BX -> current interrupt handler
SeeAlso: AH=25h,AX=2503h
----------213501-----------------------------
INT 21 P - FlashTek X-32VM - ALLOCATE PROTECTED-MODE SELECTOR
AX = 3501h
Return: CF clear if successful
BX = new selector
CF set on error (no more selectors available)
Note: the new selector will be an expand-up read/write data selector with
undefined base and limit
SeeAlso: AX=3502h,INT 31/AX=0000h
----------213502-----------------------------
INT 21 P - FlashTek X-32VM - DEALLOCATE PROTECTED-MODE SELECTOR
AX = 3502h
BX = selector
Return: CF clear if successful
CF set on error (invalid selector)
Note: only selectors allocated via AX=3501h should be deallocated
SeeAlso: AX=3501h,INT 31/AX=0001h
----------213503-----------------------------
INT 21 P - FlashTek X-32VM - SET SELECTOR BASE ADDRESS
AX = 3503h
BX = selector
ECX = base address
Return: CF clear if successful
CF set on error (invalid selector)
Note: there are probably additional 35xxh functions, but the message
containing the FlashTek calls was truncated in transit and the
remaining information did not arrive prior to release
SeeAlso: INT 31/AX=0007h
----------21357F-----------------------------
INT 21 - VIRUS - "Agiplan"/"Month 4-6" - INSTALLATION CHECK
AX = 357Fh
Return: DX = FFFFh if installed
SeeAlso: AX=33E0h,AX=3DFFh
----------2136-------------------------------
INT 21 - DOS 2+ - GET FREE DISK SPACE
AH = 36h
DL = drive number (00h = default, 01h = A:, etc)
Return: AX = FFFFh if invalid drive
else
AX = sectors per cluster
BX = number of free clusters
CX = bytes per sector
DX = total clusters on drive
Notes: free space on drive in bytes is AX * BX * CX
total space on drive in bytes is AX * CX * DX
"lost clusters" are considered to be in use
according to Dave Williams' MSDOS reference, the value in DX is
incorrect for non-default drives after ASSIGN is run
SeeAlso: AH=1Bh,AH=1Ch
----------213700-----------------------------
INT 21 - DOS 2+ - "SWITCHAR" - GET SWITCH CHARACTER
AX = 3700h
Return: AL = status
00h successful
DL = current switch character
FFh unsupported subfunction
Desc: Determine the character which is used to introduce command switches.
This setting is ignored by DOS commands in version 4.0 and higher,
but is honored by many third-party programs.
Notes: documented in some OEM versions of some releases of DOS
supported by OS/2 compatibility box
always returns DL=2Fh for DOS 5.0
SeeAlso: AX=3701h
----------213701-----------------------------
INT 21 - DOS 2+ - "SWITCHAR" - SET SWITCH CHARACTER
AX = 3701h
DL = new switch character
Return: AL = status
00h successful
FFh unsupported subfunction
Notes: documented in some OEM versions of some releases of DOS
supported by OS/2 compatibility box
ignored by DOS 5.0
SeeAlso: AX=3700h
----------2137-------------------------------
INT 21 - DOS 2.x and 3.3+ only - "AVAILDEV" - SPECIFY \DEV\ PREFIX USE
AH = 37h
AL = subfunction
02h get availdev flag
Return: DL = 00h \DEV\ must precede character device names
= nonzero \DEV\ is optional
03h set availdev flag
DL = 00h \DEV\ is mandatory
= nonzero \DEV\ is optional
Return: AL = status
00h successful
FFh unsupported subfunction
Notes: all versions of DOS from 2.00 allow \DEV\ to be prepended to device
names without generating an error even if the directory \DEV does
not actually exist (other paths generate an error if they do not
exist).
although DOS 3.3+ accepts these calls, they have no effect, and
AL=02h always returns DL=FFh
----------2138-------------------------------
INT 21 - DOS 2+ - GET COUNTRY-SPECIFIC INFORMATION
AH = 38h
--DOS 2.x--
AL = 00h get current-country info
DS:DX -> buffer for returned info (see below)
Return: CF set on error
AX = error code (02h)
CF clear if successful
AX = country code (MSDOS 2.11 only)
buffer at DS:DX filled
--DOS 3+--
AL = 00h for current country
AL = 01h thru 0FEh for specific country with code <255
AL = 0FFh for specific country with code >= 255
BX = 16-bit country code
DS:DX -> buffer for returned info (see below)
Return: CF set on error
AX = error code (02h)
CF clear if successful
BX = country code
DS:DX buffer filled
SeeAlso: AH=65h,INT 10/AX=5001h,INT 2F/AX=110Ch,INT 2F/AX=1404h
Format of PCDOS 2.x country info:
Offset Size Description
00h WORD date format 0 = USA mm dd yy
1 = Europe dd mm yy
2 = Japan yy mm dd
02h BYTE currency symbol
03h BYTE 00h
04h BYTE thousands separator char
05h BYTE 00h
06h BYTE decimal separator char
07h BYTE 00h
08h 24 BYTEs reserved
Format of MSDOS 2.x,DOS 3+ country info:
Offset Size Description
00h WORD date format (see above)
02h 5 BYTEs ASCIZ currency symbol string
07h 2 BYTEs ASCIZ thousands separator
09h 2 BYTEs ASCIZ decimal separator
0Bh 2 BYTEs ASCIZ date separator
0Dh 2 BYTEs ASCIZ time separator
0Fh BYTE currency format
bit 2 = set if currency symbol replaces decimal point
bit 1 = number of spaces between value and currency symbol
bit 0 = 0 if currency symbol precedes value
1 if currency symbol follows value
10h BYTE number of digits after decimal in currency
11h BYTE time format
bit 0 = 0 if 12-hour clock
1 if 24-hour clock
12h DWORD address of case map routine
(FAR CALL, AL = character to map to upper case [>= 80h])
16h 2 BYTEs ASCIZ data-list separator
18h 10 BYTEs reserved
Values for country code:
001h United States
002h Canadian-French
003h Latin America
01Fh Netherlands
020h Belgium
021h France
022h Spain
024h Hungary (not supported by DR-DOS 5.0)
026h Yugoslavia (not supported by DR-DOS 5.0)
027h Italy
029h Switzerland
02Ah Czechoslovakia (not supported by DR-DOS 5.0)
02Bh Austria (DR-DOS 5.0)
02Ch United Kingdom
02Dh Denmark
02Eh Sweden
02Fh Norway
030h Poland (not supported by DR-DOS 5.0)
031h Germany
037h Brazil (not supported by DR-DOS 5.0)
03Dh International English [Australia in DR-DOS 5.0]
051h Japan (DR-DOS 5.0)
052h Korea (DR-DOS 5.0)
15Fh Portugal
166h Finland
311h Middle East (DR-DOS 5.0)
3CCh Israel (DR-DOS 5.0)
----------2138-------------------------------
INT 21 - DOS 3+ - SET COUNTRY CODE
AH = 38h
AL = 01h thru 0FEh for specific country with code <255
AL = FFh for specific country with code >= 255
BX = 16-bit country code
DX = FFFFh
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: not supported by OS/2
SeeAlso: INT 2F/AX=1403h
----------2139-------------------------------
INT 21 - DOS 2+ - "MKDIR" - CREATE SUBDIRECTORY
AH = 39h
DS:DX -> ASCIZ pathname
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h) (see AH=59h)
Notes: all directories in the given path except the last must exist
fails if the parent directory is the root and is full
DOS 2.x-3.3 allow the creation of a directory sufficiently deep that
it is not possible to make that directory the current directory
because the path would exceed 64 characters
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=3Ah,AH=3Bh,AH=E2h/SF=0Ah,INT 2F/AX=1103h
----------213A-------------------------------
INT 21 - DOS 2+ - "RMDIR" - REMOVE SUBDIRECTORY
AH = 3Ah
DS:DX -> ASCIZ pathname of directory to be removed
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h,05h,06h,10h) (see AH=59h)
Notes: directory must be empty (contain only '.' and '..' entries)
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=39h,AH=3Bh,AH=E2h/SF=0Bh,INT 2F/AX=1101h
----------213B-------------------------------
INT 21 - DOS 2+ - "CHDIR" - SET CURRENT DIRECTORY
AH = 3Bh
DS:DX -> ASCIZ pathname to become current directory (max 64 bytes)
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (03h) (see AH=59h)
Notes: if new directory name includes a drive letter, the default drive is
not changed, only the current directory on that drive
changing the current directory also changes the directory in which
FCB file calls operate
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=47h,INT 2F/AX=1105h
----------213C-------------------------------
INT 21 - DOS 2+ - "CREAT" - CREATE OR TRUNCATE FILE
AH = 3CH
CX = file attribute
bit 0: read-only
1: hidden
2: system
3: volume label (ignored)
4: reserved, must be zero (directory)
5: archive bit
7: if set, file is shareable under Novell NetWare
DS:DX -> ASCIZ filename
Return: CF clear if successful
AX = file handle
CF set on error
AX = error code (03h,04h,05h) (see AH=59h)
Notes: if a file with the given name exists, it is truncated to zero length
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=16h,AH=3Dh,AH=5Ah,AH=5Bh,AH=93h
----------213D-------------------------------
INT 21 - DOS 2+ - "OPEN" - OPEN EXISTING FILE
AH = 3Dh
AL = access and sharing modes
bits 2-0: access mode
000 read only
001 write only
010 read/write
bit 3: reserved (0)
bits 6-4: sharing mode (DOS 3+)
000 compatibility mode
001 "DENYALL" prohibit both read and write access by others
010 "DENYWRITE" prohibit write access by others
011 "DENYREAD" prohibit read access by others
100 "DENYNONE" allow full access by others
bit 7: inheritance
if set, file is private to current process and will not be
inherited by child processes
DS:DX -> ASCIZ filename
CL = attribute mask of files to look for (server call only)
Return: CF clear if successful
AX = file handle
CF set on error
AX = error code (01h,02h,03h,04h,05h,0Ch) (see AH=59h)
Notes: file pointer is set to start of file
file handles which are inherited from a parent also inherit sharing
and access restrictions
files may be opened even if given the hidden or system attributes
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=0Fh,AH=3Ch,AX=4301h,AX=5D00h,INT 2F/AX=1226h
File sharing behavior:
| Second and subsequent Opens
First |Compat Deny Deny Deny Deny
Open | All Write Read None
|R W RW R W RW R W RW R W RW R W RW
- - - - -| - - - - - - - - - - - - - - - - -
Compat R |Y Y Y N N N 1 N N N N N 1 N N
W |Y Y Y N N N N N N N N N N N N
RW|Y Y Y N N N N N N N N N N N N
- - - - -|
Deny R |C C C N N N N N N N N N N N N
All W |C C C N N N N N N N N N N N N
RW|C C C N N N N N N N N N N N N
- - - - -|
Deny R |2 C C N N N Y N N N N N Y N N
Write W |C C C N N N N N N Y N N Y N N
RW|C C C N N N N N N N N N Y N N
- - - - -|
Deny R |C C C N N N N Y N N N N N Y N
Read W |C C C N N N N N N N Y N N Y N
RW|C C C N N N N N N N N N N Y N
- - - - -|
Deny R |2 C C N N N Y Y Y N N N Y Y Y
None W |C C C N N N N N N Y Y Y Y Y Y
RW|C C C N N N N N N N N N Y Y Y
Legend: Y = open succeeds, N = open fails with error code 05h
C = open fails, INT 24 generated
1 = open succeeds if file read-only, else fails with error code
2 = open succeeds if file read-only, else fails with INT 24
----------213DFF-----------------------------
INT 21 - VIRUS - "JD-448" - INSTALLATION CHECK
AX = 3DFFh
Return: AX = 4A44h if resident
SeeAlso: AX=357Fh,AX=4203h
----------213E-------------------------------
INT 21 - DOS 2+ - "CLOSE" - CLOSE FILE
AH = 3Eh
BX = file handle
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (06h) (see AH=59h)
Note: if the file was written to, any pending disk writes are performed, the
time and date stamps are set to the current time, and the directory
entry is updated
SeeAlso: AH=10h,AH=3Ch,AH=3Dh,INT 2F/AX=1106h,INT 2F/AX=1227h
----------213F-------------------------------
INT 21 - DOS 2+ - "READ" - READ FROM FILE OR DEVICE
AH = 3Fh
BX = file handle
CX = number of bytes to read
DS:DX -> buffer for data
Return: CF clear if successful
AX = number of bytes actually read (0 if at EOF before call)
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes: data is read beginning at current file position, and the file position
is updated after a successful read
the returned AX may be smaller than the request in CX if a partial
read occurred
if reading from CON, read stops at first CR
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=27h,AH=40h,AH=93h,INT 2F/AX=1108h,INT 2F/AX=1229h
----------213F-------------------------------
INT 21 - Turbo Debug HARDWARE BREAKPOINTS - READ STATUS BLOCK
AH = 3Fh
BX = handle for character device "TDHDEBUG"
CX = number of bytes to read
DS:DX -> buffer for status block (see below)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (05h,06h) (see AH=59h)
SeeAlso: AH=40h"Turbo Debug"
Format of status block:
Offset Size Description
00h BYTE status of command
00h successful
01h invalid handle
02h no more breakpoints available
03h hardware does not support specified breakpoint type
04h previous command prevents execution
05h debugger hardware not found
06h hardware failure
07h invalid command
08h driver not initialized yet
FEh recursive entry (hardware breakpoint inside hw bp handler)
---status for command 01h---
01h WORD device driver interface version number (currently 1)
03h WORD device driver software version
05h BYTE maximum simultaneous hardware breakpoints
06h BYTE configuration bits
bit 0: CPU and DMA accesses are distinct
1: can detect DMA transfers
2: supports data mask
3: hardware pass counter on breakpoints
4: can match on data as well as addresses
07h BYTE supported breakpoint types
bit 0: memory read
1: memory write
2: memory read/write
3: I/O read
4: I/O write
5: I/O read/write
6: instruction fetch
08h WORD supported addressing match modes
bit 0: any address
1: equal to test value
2: not equal
3: above test value
4: below test value
5: below or equal
6: above or equal
7: within range
8: outside range
0Ah WORD supported data matches
bit 0: any data
1: equal to test value
2: not equal
3: above test value
4: below test value
5: below or equal
6: above or equal
7: within range
8: outside range
0Ch BYTE maximum data match length (01h, 02h, or 04h)
0Dh WORD size of onboard memory (in K)
0Fh WORD maximum number of trace-back events
11h WORD hardware breakpoint enable byte address segment (0000h if not
supported)
---status for command 04h---
01h BYTE handle to use when referring to the just-set breakpoint
----------213F-------------------------------
INT 21 - PC/TCP IPCUST.SYS - READ CONFIGURATION DATA
AH = 3Fh
BX = handle for character device "$IPCUST"
CX = number of bytes to read
DS:DX -> buffer for configuration data (see below)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes: if less than the entire data is read or written, the next read/write
continues where the previous one ended; IOCTL calls AX=4402h and
AX=4403h both reset the location at which the next operation starts
to zero
the data pointer is also reset to zero if the previous read or write
reached or exceeded the end of the data, when the current function
is read and the previous was write, or vice versa
SeeAlso: AH=40h"IPCUST",AX=4402h"IPCUST"
Format of configuration data:
Offset Size Description
00h 12 BYTEs IPCUST.SYS device driver header
12h BYTE ???
13h BYTE ???
14h WORD ???
16h BYTE bit flags
bit 0: send BS rather than DEL for BackSpace key
bit 1: wrap long lines
17h BYTE ???
18h 64 BYTEs ASCIZ hostname
58h 64 BYTEs ASCIZ domain name
(fully qualified domain name is hostname.domain-name)
98h 16 BYTEs ASCIZ username
A8h 64 BYTEs ASCIZ full name
E8h 64 BYTEs ASCIZ office address
128h 32 BYTEs ASCIZ phone number
148h WORD offset from GMT in minutes
14Ah 4 BYTEs ASCIZ timezone name
14Eh WORD number of time servers
150h ? DWORDs IP addresses for time servers (big-endian)
???
164h WORD number of old-style name servers
166h 3 DWORDs IP addresses for name servers (big-endian)
172h WORD number of domain name servers
174h 3 DWORDs IP addresses for domain name servers (big-endian)
180h DWORD IP address of default gateway (big-endian)
184h DWORD IP address of log server (big-endian)
188h DWORD IP address of cookie server (big-endian)
18Ch DWORD IP address of lpr server (big-endian)
190h DWORD IP address of imagen print server
194h 54 BYTEs ???
1E8h WORD TCP default window size in bytes
1EAh WORD TCP low window size
1ECh 64 BYTEs ASCIZ host tabel filename
22Ch 2 BYTEs ???
22Eh 80 BYTEs ASCIZ mail relay host name
27Eh BYTE ???
27Fh BYTE ??? bit flags
280h 44 BYTEs ???
2ACh WORD ???
2AEh 202 BYTEs ???
----------2140-------------------------------
INT 21 - DOS 2+ - "WRITE" - WRITE TO FILE OR DEVICE
AH = 40h
BX = file handle
CX = number of bytes to write
DS:DX -> data to write
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes: if CX is zero, no data is written, and the file is truncated or
extended to the current position
data is written beginning at the current file position, and the file
position is updated after a successful write
the usual cause for AX < CX on return is a full disk
BUG: a write of zero bytes will appear to succeed when it actually failed
if the write is extending the file and there is not enough disk
space for the expanded file (DOS 5.0); one should therefore check
whether the file was in fact extended by seeking to 0 bytes from
the end of the file (INT 21/AX=4202h/CX=0/DX=0)
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=28h,AH=3Fh,AH=93h,INT 2F/AX=1109h
----------2140-------------------------------
INT 21 - Turbo Debug HARDWARE BREAKPOINTS - SEND CMD TO HARDWARE BRKPNT DRIVER
AH = 40h
BX = handle for character device "TDHDEBUG"
CX = number of bytes to write
DS:DX -> hardware breakpoint command (see below)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see AH=59h)
Note: results are retrieved by reading from the device
SeeAlso: AH=3Fh"Turbo Debug"
Format of hardware breakpoint commands:
Offset Size Description
00h BYTE command code
00h install interrupt vectors
01h get hardware capabilities
02h enable hardware breakpoints
03h disable hardware breakpoints
04h set hardware breakpoint
05h clear hardware breakpoint
06h set I/O base address and reset hardware
07h restore interrupt vectors
---command code 00h---
01h DWORD pointer to Turbo Debugger entry point to be jumped to on
hardware breakpoint; call with CPU state the same as on
the breakpoint except for pushing AX and placing an entry
code (FFh if breakout button or breakpoint handle) in AH
---command code 04h---
01h BYTE breakpoint type
00h memory read
01h memory write
02h memory read/write
03h I/O read
04h I/O write
05h I/O read/write
06h instruction fetch
02h BYTE address matching mode
00h any address
01h equal to test value
02h different from test value
03h above test value
04h below test value
05h below or equal to test value
06h above or equal to test value
07h within inclusive range
08h outside specified range
03h DWORD 32-bit linear low address
07h DWORD 32-bit linear high address
0Bh WORD pass count
0Dh BYTE data size (01h, 02h, or 04h)
0Eh BYTE source of matched bus cycle
01h CPU
02h DMA
03h either
0Fh BYTE data-matching mode
00h match any
01h equal to test value
02h different from test value
03h above test value
04h below test value
05h below or equal to test value
06h above or equal to test value
07h within specified range
08h outside specified range
10h DWORD low data value
14h DWORD high data value
18h DWORD data mask specifying which bits of the data are tested
---command code 05h---
01h BYTE handle of breakpoint to clear (breakpoint returned from command
04h)
---command code 06h---
01h WORD base address of hardware debugger board
----------2140-------------------------------
INT 21 - PC/TCP IPCUST.SYS - WRITE CONFIGURATION DATA
AH = 40h
BX = handle for character device "$IPCUST"
CX = number of bytes to write
DS:DX -> buffer for configuration data (AH=3Fh"IPCUST")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes: if less than the entire data is read or written, the next read/write
continues where the previous one ended; IOCTL calls AX=4402h and
AX=4403h both reset the location at which the next operation starts
to zero
the data pointer is also reset to zero if the previous read or write
reached or exceeded the end of the data, when the current function
is read and the previous was write, or vice versa
SeeAlso: AH=3Fh"IPCUST",AX=4402h"IPCUST"
----------214000BX0002-----------------------
INT 21 - FARTBELL.EXE - INSTALLATION CHECK
AX = 4000h
BX = 0002h
CX = 0000h
DS:DX = 0000h:0000h
Return: CF clear if installed
AX = CS of resident code
Note: FARTBELL is a joke program by Guenther Thiele which makes various
noises when programs output a bell
SeeAlso: AX=4001h
----------214001BX0002-----------------------
INT 21 - FARTBELL.EXE - FORCE NOISE
AX = 4001h
BX = 0002h
CX = 0000h
DS:DX = 0000h:0000h
Note: FARTBELL is a joke program by Guenther Thiele which makes various
noises when programs output a bell
SeeAlso: AX=4000h
----------2141-------------------------------
INT 21 - DOS 2+ - "UNLINK" - DELETE FILE
AH = 41h
DS:DX -> ASCIZ filename (no wildcards, but see below)
CL = attribute mask for deletion (server call only, see below)
Return: CF clear if successful
AX destroyed (DOS 3.3) AL seems to be drive of deleted file
CF set on error
AX = error code (02h,03h,05h) (see AH=59h)
Notes: (DOS 3.1+) wildcards are allowed if invoked via AX=5D00h, in which case
the filespec must be canonical (as returned by AH=60h), and only
files matching the attribute mask in CL are deleted
DOS does not erase the file's data; it merely becomes inaccessible
because the FAT chain for the file is cleared
deleting a file which is currently open may lead to filesystem
corruption. Unless SHARE is loaded, DOS does not close the handles
referencing the deleted file, thus allowing writes to a nonexistant
file.
under DRDOS and DR Multiuser DOS, this function will fail if the file
is currently open
under the FlashTek X-32 DOS extender, the pointer is in DS:EDX
SeeAlso: AH=13h,AX=4301h,AX=5D00h,AH=60h,AX=F244h,INT 2F/AX=1113h
----------214101DXFFFE-----------------------
INT 21 - SoftLogic Data Guardian - ???
AX = 4101h
DX = FFFEh
Return: AX = 0000h if installed
Note: resident code sets several internal variables on this call
----------2142-------------------------------
INT 21 - DOS 2+ - "LSEEK" - SET CURRENT FILE POSITION
AH = 42h
AL = origin of move
00h start of file
01h current file position
02h end of file
BX = file handle
CX:DX = offset from origin of new file position
Return: CF clear if successful
DX:AX = new file position in bytes from start of file
CF set on error
AX = error code (01h,06h) (see AH=59h)
Notes: for origins 01h and 02h, the pointer may be positioned before the
start of the file; no error is returned in that case, but subsequent
attempts at I/O will produce errors
if the new position is beyond the current end of file, the file will
be extended by the next write (see AH=40h)
SeeAlso: AH=24h,INT 2F/AX=1228h
----------214203-----------------------------
INT 21 - VIRUS - "Shake" - INSTALLATION CHECK
AX = 4203h
Return: AX = 1234h if resident
SeeAlso: AX=3DFFh,AX=4243h
----------214243-----------------------------
INT 21 - VIRUS - "Invader" - INSTALLATION CHECK
AX = 4243h
Return: AX = 5678h if resident
SeeAlso: AX=4203h,AX=4B04h
----------214300-----------------------------
INT 21 - DOS 2+ - GET FILE ATTRIBUTES
AX = 4300h
DS:DX -> ASCIZ filename
Return: CF clear if successful
CX = attributes (see AX=4301h)
AX = CX (DR-DOS 5.0)
CF set on error
AX = error code (01h,02h,03h,05h) (see AH=59h)
Note: under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
SeeAlso: AX=4301h,AX=4310h,AH=B6h,INT 2F/AX=110Fh
----------214301-----------------------------
INT 21 - DOS 2+ - "CHMOD" - SET FILE ATTRIBUTES
AX = 4301h
CX = new attributes
bit 7: shareable (Novell NetWare)
6: unused
5: archive
4: directory
3: volume label
execute-only (Novell NetWare)
2: system
1: hidden
0: read-only
DS:DX -> ASCIZ filename
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,02h,03h,05h) (see AH=59h)
Notes: will not change volume label or directory attribute bits, but will
change the other attribute bits of a directory (the directory
bit must be cleared to successfully change the other attributes of a
directory, but the directory will not be changed to a normal file as
a result)
MSDOS 4.01 reportedly closes the file if it is currently open
for security reasons, the Novell NetWare execute-only bit can never
be cleared; the file must be deleted and recreated
under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
SeeAlso: AX=4300h,AX=4311h,INT 2F/AX=110Eh
----------214302-----------------------------
INT 21 - DR-DOS 3.41+ internal - GET ACCESS RIGHTS
AX = 4302h
DS:DX -> ASCIZ pathname
Return: CF clear if successful
CX = access rights
bit 0 owner delete requires password
bit 1 owner execution requires password (FlexOS)
bit 2 owner write requires password
bit 3 owner read requires password
bit 4 group delete requires password
bit 5 group execution requires password (FlexOS)
bit 6 group write requires password
bit 7 group read requires password
bit 8 world delete requires password
bit 9 world execution requires password (FlexOS)
bit 10 world write requires password
bit 11 world read requires password
AX = CX (DR-DOS 5.0)
CF set on error
AX = error code
Desc: Determine which operations the calling program may perform on a
specified file without being required to provide a password.
Notes: this protection scheme has been coordinated on all current Digital
Research/Novell operating systems (DR-DOS 3.41+, DRMDOS 5.x, and
FlexOS 2+)
only FlexOS actually uses the "execution" bits; DR-DOS 3.41+ treats
them as "read" bits.
DR-DOS 3.41-5.x only use bits 0-3. Only DR-DOS 6.0 using a
DRMDOS 5.x security system allowing for users and groups uses bits
4-11.
SeeAlso: AX=4303h
----------214303-----------------------------
INT 21 - DR-DOS 3.41+ internal - SET ACCESS RIGHTS AND PASSWORD
AX = 4303h
CX = access rights
bits 11-0: access rights (see AX=4302h)
bit 15: new password is to be set
DS:DX -> ASCIZ pathname
[DTA] = new password if CX bit 15 is set (blank-padded to 8 characters)
Return: CF clear if successful
CF set on error
AX = error code
Note: if the file is already protected, the old password must be added after
the pathname, separated by a ";"
SeeAlso: AX=4302h,AX=4454h
----------214304-----------------------------
INT 21 - DR-DOS 5.0 internal - GET ???
AX = 4304h
???
Return: CF clear if successful
CX = AX = ???
CF set on error
AX = error code (see AH=59h)
SeeAlso: AX=4305h
----------214305-----------------------------
INT 21 - DR-DOS 5.0 internal - SET ???
AX = 4305h
???
Return: CF clear if successful
CF set on error
AX = error code (see AH=59h)
SeeAlso: AX=4304h
----------214310-----------------------------
INT 21 - Banyan VINES 2.1+ - GET EXTENDED FILE ATTRIBUTES
AX = 4310h
DS:DX -> ASCIZ filename
Return: CF clear if successful
CH = attributes (see AX=4311h)
CF set on error
AX = error code (01h,02h,03h,05h) (see AH=59h)
Note: the filename may be a directory but must be on a VINES file service
SeeAlso: AX=4300h,AX=4311h,AH=B6h,INT 2F/AX=110Fh
----------214310-----------------------------
INT 21 - Banyan VINES 2.1+ - SET EXTENDED FILE ATTRIBUTES
AX = 43100h
CH = new attributes
bit 7: unused
bit 6: shareable
bit 5: execute-only
bits 4-0: unused
DS:DX -> ASCIZ filename
Return: CF clear if successful
CF set on error
AX = error code (01h,02h,03h,05h) (see AH=59h)
Note: the filename may be a directory but must be on a VINES file service
SeeAlso: AX=4301h,AX=4310h,INT 2F/AX=110Eh
----------214400-----------------------------
INT 21 - DOS 2+ - IOCTL - GET DEVICE INFORMATION
AX = 4400h
BX = handle
Return: CF clear if successful
DX = device information word
character device
14: device driver can process IOCTL requests (see AX=4402h)
13: output until busy supported
11: driver supports OPEN/CLOSE calls
7: set (indicates device)
6: EOF on input
5: raw (binary) mode
4: device is special (uses INT 29)
3: clock device
2: NUL device
1: standard output
0: standard input
disk file
15: file is remote (DOS 3+)
14: don't set file date/time on closing (DOS 3+)
11: media not removable
8: (DOS 4+) generate INT 24 if no disk space on write
7: clear (indicates file)
6: file has not been written
5-0: drive number (0 = A:)
AX destroyed
CF set on error
AX = error code (01h,05h,06h) (see AH=59h)
Note: value in DH corresponds to high byte of device driver's attribute word
if handle refers to a character device
SeeAlso: AX=4401h,INT 2F/AX=122Bh
----------214401-----------------------------
INT 21 - DOS 2+ - IOCTL - SET DEVICE INFORMATION
AX = 4401h
BX = handle (must refer to character device)
DX = device information word (see AX=4400h)
(DH must be zero)
Return: CF clear if successful
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4400h,INT 2F/AX=122Bh
----------214402-----------------------------
INT 21 - DOS 2+ - IOCTL - READ FROM CHARACTER DEVICE CONTROL CHANNEL
AX = 4402h
BX = file handle referencing character device
CX = number of bytes to read
DS:DX -> buffer
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: format of data is driver-specific (see below for some specific cases)
SeeAlso: AX=4400h,AX=4403h,AX=4404h,INT 2F/AX=122Bh
----------214402-----------------------------
INT 21 - Network Driver Interface Spec 2.0.1 - PROTOCOL MANAGER
AX = 4402h
BX = file handle for device "PROTMAN$"
DS:DX -> request block (see below)
CX = 000Eh (size of request block)
Format of request block for GetProtocolManagerInfo:
Offset Size Description
00h WORD 01h
02h WORD returned status (see below)
04h DWORD returned pointer to structure representing parsed user config
08h DWORD unused
0Ch WORD returned BCD version of NDIS on which Protocol Manager is based
Format of request block for RegisterModule:
Offset Size Description
00h WORD 02h
02h WORD returned status (see below)
04h DWORD pointer to module's common characteristics table (see below)
08h DWORD pointer to list of modules to which the module is to be bound
0Ch WORD unused
Format of request block for BindAndStart:
Offset Size Description
00h WORD 03h
02h WORD returned status (see below)
04h DWORD caller's virtual address in FailingModules structure
08h DWORD unused
0Ch WORD unused
Format of request block for GetProtocolManagerLinkage:
Offset Size Description
00h WORD 04h
02h WORD returned status (see below)
04h DWORD returned dispatch point
08h DWORD unused
0Ch WORD returned protocol manager DS
Note: the dispatch point may be called as follows instead of using this IOCTL
STACK: WORD protocol manager DS
DWORD pointer to request block
Return: AX = returned status
STACK popped
Format of request block for GetProtocolIniPath:
Offset Size Description
00h WORD 05h
02h WORD returned status (see below)
04h DWORD pointer to a buffer for the ASCIZ pathname of PROTOCOL.INI
08h DWORD unused
0Ch WORD buffer length
Format of request block for RegisterProtocolManagerInfo:
Offset Size Description
00h WORD 06h
02h WORD returned status (see below)
04h DWORD pointer to structure containing parsed user config file
08h DWORD unused
0Ch WORD length of structure
Format of request block for InitAndRegister:
Offset Size Description
00h WORD 07h
02h WORD returned status (see below)
04h DWORD unused
08h DWORD poitner to ASCIZ name of the module to be prebind initialized
0Ch WORD unused
Format of request block for UnbindAndStop:
Offset Size Description
00h WORD 08h
02h WORD returned status (see below)
04h DWORD failing modules as for BindAndStart
08h DWORD if not 0000h:0000h, pointer to ASCIZ name of module to unbind
if 0000h:0000h, terminate a set of previously dynamically
bound protocol modules
0Ch WORD unused
Format of request block for BindStatus:
Offset Size Description
00h WORD 09h
02h WORD returned status (see below)
04h DWORD must be 0000h:0000h
on return, points to root tree
08h DWORD 0000h:0000h
0Ch WORD unused under DOS
Format of request block for RegisterStatus:
Offset Size Description
00h WORD 0Ah
02h WORD returned status (0000h, 0008h, 002Ch) (see below)
04h DWORD 0000h:0000h
08h DWORD pointer to 16-byte ASCIZ module name
0Ch WORD 0000h
Values of status code:
0000h success
0001h wait for release--protocol has retained control of the data buffer
0002h request queued
0003h frame not recognized
0004h frame rejected
0005h frame should be forwarded
0006h out of resource
0007h invalid parameter
0008h invalid function
0009h not supported
000Ah hardware error
000Bh transmit error
000Ch unrecognized destination
000Dh buffer too small
0020h already started
0021h binding incomplete
0022h driver not initialized
0023h hardware not found
0024h hardware failure
0025h configuration failure
0026h interrupt conflict
0027h MAC incompatible
0028h initialization failed
0029h no binding
002Ah network may be disconnected
002Bh incompatible OS version
002Ch already registered
002Dh path not found
002Eh insufficient memory
002Fh info not found
00FFh general failure
F000h-FFFFh reserved for vendor-specific codes, treated as general failure
Format of common characteristics table:
Offset Size Description
00h WORD size of table in bytes
02h BYTE NDIS major version
03h BYTE NDIS minor version
04h WORD reserved
06h BYTE module major version
07h BYTE module minor version
08h DWORD module function flag bits
bit 0: binding at upper boundary supported
bit 1: binding at lower boundary supported
bit 2: dynamically bound
bits 3-31 reserved, must be 0
0Ch 16 BYTEs ASCIZ module name
1Ch BYTE upper boundary protocol level
01h Media Access Control
02h Data link
03h network
04h transport
05h session
FFh not specified
1Dh BYTE upper boundary interface type
for MACs: 1 = MAC
for data links and transports: to be defined
for session: 1 = NCB
any level: 0 = private (ISV-defined)
1Eh BYTE lower boundary protocol level
00h physical
01h Media Access Control
02h Data link
03h network
04h transport
05h session
FFh not specified
1Fh BYTE lower boundary interface type
same as offset 1Dh
20h WORD module ID filled in by protocol manager
22h WORD module DS
24h DWORD system request entry point
28h DWORD pointer to service-specific characteristics
0000h:0000h if none
2Ch DWORD pointer to service-specific status
0000h:0000h if none
30h DWORD pointer to upper dispatch table (see below)
0000h:0000h if none
34h DWORD pointer to lower dispatch table (see below)
0000h:0000h if none
38h DWORD reserved, must be 0
3Ch DWORD reserved, must be 0
Note: for compatibility with NDIS 1.x.x, a major version of 00h is
interpreted as 01h
Format of MAC Service-Specific Characteristics Table:
Offset Size Description
00h WORD length of table in bytes
02h 16 BYTEs ASCIZ MAC type name, "802.3", "802.4", "802.5", "802.6", "DIX",
"DIX+802.3", "APPLETALK", "ARCNET", "FDDI", "SDLC", "BSC",
"HDLC", or "ISDN"
12h WORD length of station addresses in bytes
14h 16 BYTEs permanent station address
24h 16 BYTEs current station address
34h DWORD current functional adapter address (00000000h if none)
38h DWORD pointer to multicast address list
3Ch DWORD link speed in bits/sec
40h DWORD service flags
bit 0: supports broadcast
1: supports multicast
2: supports functional/group addressing
3: supports promiscuous mode
4: station address software settable
5: statistics always current
6: supports InitiateDiagnostics
7: supports loopback
8: MAC does primarily ReceiveChain indications instead of
ReceiveLookahead indications
9: supports IBM source routing
10: supports MAC reset
11: supports Open/Close adapter
12: supports interrupt request
13: supports source routing bridge
14: supports GDT virtual addresses (OS/2 version)
15: multiple TransferDatas allowed durign a single
indication
16: MAC normally sets FrameSize = 0 in ReceiveLookahead
17-31: reserved, must be 0
44h WORD maximum frame size which may be both sent and received
46h DWORD total transmit buffer capacity in bytes
4Ah WORD transmit buffer allocation block size in bytes
4Ch DWORD total receive buffer capacity in bytes
50h WORD receive buffer allocation block size in bytes
52h 3 BYTEs IEEE vendor code
55h BYTE vendor adapter code
56h DWORD pointer to ASCIZ vendor adapter description
5Ah WORD IRQ used by adapter
5Ch WORD transmit queue depth
5Eh WORD maximum supported number of data blocks in buffer descriptors
60h N BYTEs vendor-specific info
Format of NetBIOS Service-Specific Characteristics Table
Offset Size Description
00h WORD length of table in bytes
02h 16 BYTEs ASCIZ type name of NetBIOS module
12h WORD NetBIOS module code
14h N BYTEs vendor-specific info
Format of MAC Service-Specific Status Table:
Offset Size Description
00h WORD length of table in bytes
02h DWORD seconds since 0:00 1/1/70 when diagnostics last run
(FFFFFFFFh = never)
06h DWORD MAC status bits
bits 0-2: 000 hardware not installed
001 hardware failed startup diagnostics
010 hardware configuration problem
011 hardware fault
100 operating marginally due to soft faults
101 reserved
110 reserved
111 hardware fully operational
bit 3: MAC bound
4: MAC open
5: diagnostics in progress
6-31: reserved
0Ah WORD current packet filter flags
bit 0: directed/multicast or group/functional
1: broadcast
2: promiscuous
3: all source routing
4-15: reserved, must be zero
0Ch DWORD pointer to media-specific status table or 0000h:0000h
10h DWORD seconds past 0:00 1/1/70 of last ClearStatistics
14h DWORD total frames received (FFFFFFFFh = not counted)
18h DWORD frames with CRC error (FFFFFFFFh = not counted)
1Ch DWORD total bytes received (FFFFFFFFh = not counted)
20h DWORD frames discarded--no buffer space (FFFFFFFFh = not counted)
24h DWORD multicast frames received (FFFFFFFFh = not counted)
28h DWORD broadcast frames received (FFFFFFFFh = not counted)
2Ch DWORD frames with errors (FFFFFFFFh = not counted)
30h DWORD overly large frames (FFFFFFFFh = not counted)
34h DWORD frames less than minimum size (FFFFFFFFh = not counted)
38h DWORD multicast bytes received (FFFFFFFFh = not counted)
3Ch DWORD broadcast bytes received (FFFFFFFFh = not counted)
40h DWORD frames discarded--hardware error (FFFFFFFFh = not counted)
44h DWORD total frames transmitted (FFFFFFFFh = not counted)
48h DWORD total bytes transmitted (FFFFFFFFh = not counted)
4Ch DWORD multicast frames transmitted (FFFFFFFFh = not counted)
50h DWORD broadcast frames transmitted (FFFFFFFFh = not counted)
54h DWORD broadcast bytes transmitted (FFFFFFFFh = not counted)
58h DWORD multicast bytes transmitted (FFFFFFFFh = not counted)
5Ch DWORD frames not transmitted--timeout (FFFFFFFFh = not counted)
60h DWORD frames not transmitted--hardware error (FFFFFFFFh = not countd)
64h N BYTEs vendor-specific info
----------214402-----------------------------
INT 21 U - IBM SYSTEM 36/38 WORKSTATION EMULATION - VDI.SYS - GET ???
AX = 4402h
BX = handle for character device "GDMS"
CX = number of bytes to read (>= 4)
DS:DX -> buffer (see below)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
AX = number of bytes read
Format of returned data:
Offset Size Description
00h 4 BYTEs ???
04h DWORD pointer to ???
08h 4 BYTEs ???
----------214402-----------------------------
INT 21 U - LASTBYTE.SYS v1.19 - IOCTL - GET ??? TABLE
AX = 4402h
BX = handle for device "LA$TBYTE"
CX = 0004h
DS:DX -> DWORD to hold address of 39-byte table of ???
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
AX = number of bytes read
Note: LASTBYTE.SYS is part of "The Last Byte" by Key Software Products
SeeAlso: AX=4402h"HIGHUMM"
----------214402-----------------------------
INT 21 - HIGHUMM.SYS v1.17+ - IOCTL - GET API ADDRESS
AX = 4402h
BX = handle for device "KSP$UMM"
CX = 0004h
DS:DX -> DWORD to hold entry point
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
AX = number of bytes read
Note: HIGHUMM.SYS is part of "The Last Byte" by Key Software Products
SeeAlso: AX=4402h"LASTBYTE"
Call HIGHUMM.SYS entry point with:
AH = 00h allocate UMB (same as XMS function 10h) (see INT 2F/AX=4310h)
DX = size in paragraphs
Return: BX = segment number (if successful)
DX = size of requested block/size of largest block
AH = 01h deallocate UMB (same as XMS func 11h) (see INT 2F/AX=4310h)
DX = segment number of UMB
AH = 02h request a bank-switched memory block
DX = size in paragraphs
Return: BX = segment number (if successful)
DX = size of requested block/size of largest block
AH = 03h release a bank-switched memory block
DX = segment number
AH = 04h transfer data to/from high memory
DS:SI -> source
ES:DI -> destination
CX = length in bytes
Note: enables bank-switched memory, does the copy, then disables
bank-switched memory
AH = 05h get a word from bank-switched memory
ES:DI -> word to read
Return: DX = word
AH = 06h put a word to bank-switched memory
ES:DI -> word to write
DX = word
AH = 07h put a byte to bank-switched memory
ES:DI -> byte to write
DL = byte
AH = 08h enable bank-switched memory
DS:SI -> 6-byte status save area
AH = 09h disable bank-switched memory
DS:SI -> 6-byte save area from enable call (AH=08h)
AH = 0Ah assign name to UMB or high bank-switched block
DX = segment number
DS:SI -> 8-byte blank-padded name
AH = 0Bh locate UMB block by name
DS:SI -> 8-byte blank-padded name
Return: BX = segment number (if successful)
DX = size of block
AH = 0Ch locate bank-switched block by name
DS:SI -> 8-byte blank-padded name
Return: BX = segment number (if successful)
DX = size of block
Return: AX = status code
0001h successful
0000h failed
BL = error code
80h not implemented
B0h insufficient memory, smaller block available
B1h insufficient memory, no blocks available
B2h invalid segment number
Note: only functions 00h and 01h are always available; the remaining
functions are only enabled if the proper commandline switch is given
----------214402-----------------------------
INT 21 - SMARTDRV.SYS - IOCTL - GET CACHE STATUS
AX = 4402h
BX = file handle for device "SMARTAAR"
CX = number of bytes to read (min 28h)
DS:DX -> buffer for status record (see below)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4403h"SMARTDRV",INT 2F/AX=4A10h
Format of SMARTDRV status record:
Offset Size Description
00h BYTE write-through flag (always 01h)
01h BYTE writes should be buffered (always 00h)
02h BYTE cache enabled if 01h
03h BYTE driver type (01h extended memory, 02h expanded)
04h WORD clock ticks between cache flushes (currently unused)
06h BYTE cache contains locked tracks if nonzero
07h BYTE flush cache on INT 19 reboot if nonzero
08h BYTE cache full track writes if nonzero
09h BYTE double buffering (for VDS) state (00h off, 01h on, 02h dynamic)
0Ah DWORD original INT 13 vector
0Eh BYTE minor version number
0Fh BYTE major version number
10h WORD unused
12h WORD sectors read \
14h WORD sectors already in cache > may be scaled rather than
16h WORD sectors already in track buffer / absolute counts
18h BYTE cache hit rate in percent
19h BYTE track buffer hit rate in percent
1Ah WORD total tracks in cache
1Ch WORD number of tracks in use
1Eh WORD number of locked tracks
20h WORD number of dirty tracks
22h WORD current cache size in 16K pages
24h WORD original (maximum) cache size in 16K pages
26h WORD minimum cache size in 16K pages
28h DWORD pointer to byte flag to increment for locking cache contents
----------214402-----------------------------
INT 21 - CD-ROM device driver - IOCTL INPUT
AX = 4402h
BX = file handle referencing character device for CD-ROM driver
CX = number of bytes to read
DS:DX -> control block (see below)
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: the data returned depends on the first byte of the control block; the
remainder of the control block is filled by the driver
SeeAlso: AX=4403h"CD-ROM",INT 2F/AX=0802h
Format of control block:
Offset Size Description
00h BYTE data being requested
00h device driver header address
01h drive head location
02h reserved
03h error statistics
04h audio channel info
05h raw drive bytes (uninterpreted and device-specific)
06h device status
07h sector size
08h volume size
09h media change status
0Ah audio disk info
0Bh audio track info
0Ch audio Q-Channel info
0Dh audio sub-channel info
0Eh UPC code
---function 00h---
01h DWORD device driver header address (see also AH=52h)
---function 01h---
01h BYTE addressing mode
00h HSG
01h Red Book
02h DWORD current location of drive's head
logical sector number in HSG mode
frame/second/minute/unused in Red Book mode
(HSG sector = minute * 4500 + second * 75 + frame - 150)
---function 03h---
01h N BYTEs undefined as of 5 Aug 88 specification
---function 04h---
01h BYTE input channel (0-3) for output channel 0
02h BYTE volume for output channel 0
03h BYTE input channel (0-3) for output channel 1
04h BYTE volume for output channel 1
05h BYTE input channel (0-3) for output channel 2
06h BYTE volume for output channel 2
07h BYTE input channel (0-3) for output channel 3
08h BYTE volume for output channel 3
Notes: output channels 0 and 1 are left and right, 2 and 3 are left prime and
right prime; a volume of 00h is off
the default setting is for each input channel to be assigned to the
same-numbered output channel at full (FFh) volume
---function 05h---
01h BYTE number of bytes read
02h 128 BYTEs buffer for drive bytes
---function 06h---
01h DWORD device parameters
bit 0: door open
1: door unlocked
2: supports raw reading in addition to cooked
3: writable
4: can play audio/video tracks
5: supports interleaving
6: reserved
7: supports prefetch requests
8: supports audio channel control
9: supports Red Book addressing in addition to HSG
10: audio is playing
---function 07h---
01h BYTE read mode
00h cooked
01h raw
02h WORD sector size in bytes
---function 08h---
01h DWORD volume size in sectors
---function 09h---
01h BYTE media change status
00h don't know
01h media unchanged
FFh media has been changed
---function 0Ah---
01h BYTE lowest audio track number
02h BYTE highest audio track number
03h DWORD start address of lead-out track (Red Book format)
--function 0Bh---
01h BYTE track number (set by caller)
02h DWORD starting point of track (Red Book format)
06h BYTE track control info
bits 15,14,12: track type (notice: bits not contiguous!)
000 two audio channels, no pre-emphasis
001 two audio channels with pre-emphasis
010 data track
100 four audio channels, no pre-emphasis
101 four audio channels with pre-emphasis
other reserved
bit 13: digital copy permitted
---function 0Ch---
01h BYTE CONTROL and ADR byte (as received from drive)
02h BYTE track number
03h BYTE point or index
04h BYTE minute \
05h BYTE second > running time within track
06h BYTE frame /
07h BYTE zero
08h BYTE "AMIN" or "PMIN" \
09h BYTE "ASEC" or "PSEC" > running time on disk
0Ah BYTE "AFRAME" or "PFRAME" /
---function 0Dh---
01h DWORD starting frame address (Red Book format)
05h DWORD transfer address
09h DWORD number of sectors to read
Note: copies 96 bytes of sub-channel info per sector into buffer
---function 0Eh---
01h BYTE CONTROL and ADR byte
02h 7 BYTEs UPC/EAN code (13 BCD digits,low-order nybble of last byte is 0)
09h BYTE zero
0Ah BYTE "AFRAME"
----------214402-----------------------------
INT 21 U - Quarterdeck - QEMM-386 v5+ - GET API ENTRY POINT
AX = 4402h
BX = file handle for device "QEMM386$"
CX = 0004h
DS:DX -> DWORD buffer for API entry point
Return: CF clear if successful
buffer filled (see INT 67/AH=3Fh for entry point parameters)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"HOOKROM",INT 2F/AX=D201h/BX=5145h,INT 67/AH=3Fh
----------214402-----------------------------
INT 21 U - Quarterdeck - QEMM-386 v6+ - GET ???
AX = 4402h
BX = file handle for device "EMMXXXX0"
CX = 0006h (size of buffer in bytes)
DS:DX -> buffer for ???
first byte must be 01h on entry
Return: CF clear if successful
buffer filled (see INT 67/AH=3Fh function 1B00h)
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: this call always returns an error if Windows3 support has been disabled
with the NW3 switch to QEMM386.SYS
SeeAlso: INT 2F/AX=D201h/BX=5145h,INT 67/AH=3Fh
----------214402-----------------------------
INT 21 U - Quarterdeck - HOOKROM.SYS - GET HOOKED VECTOR TABLE
AX = 4402h
BX = file handle for device "HOOKROM$"
CX = 0004h
DS:DX -> DWORD buffer for address of hooked vector table (see below)
Return: CF clear if successful
DS:DX buffer filled
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"QEMM"
Format of hooked vector table entry:
Offset Size Description
00h 5 BYTEs FAR jump to actual interrupt handler
(end of table if first byte is not EAh)
05h BYTE interrupt vector number
----------214402-----------------------------
INT 21 - Advanced SCSI Programming Interface (ASPI) - INTERFACE
AX = 4402h
BX = file handle for device "SCSIMGR$"
CX = 0004h
DS:DX -> buffer for function address
Return: CF clear if successful
AX = 0004h
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: the function address is called with the address of a SCSI Request
Block on the stack and the caller must clean up the stack
SeeAlso: AX=440Ch"ASPITAPE",INT 11/AH=FFh"WD7000"
Format of SCSI Request Block (64 bytes):
Offset Size Description
00h BYTE request number
00h "HA_INQ" host adapter inquiry
01h "GET_TYPE" get device type
02h "EXEC_SIO" execute SCSI I/O
03h "ABORT_SRB" abort SRB
04h "RESET_DEV" reset SCSI device
05h "SET_HAPRMS" set host adapter parameters
01h BYTE request status
00h not done yet
02h aborted
04h SCSI I/O error
80h invalid
81h no adapter
82h no device attached
else status
02h BYTE host adapter ID
03h BYTE request flags
bit 3: ???
04h DWORD reserved
---request 00h---
08h BYTE (returned) number of host adapters
09h BYTE (returned) target adapter ID
0Ah 16 BYTEs (returned) manager ID
1Ah 16 BYTEs (returned) adapter ID
2Ah 16 BYTEs (returned) parameters
---request 01h---
08h BYTE target ID
09h BYTE logical unit number
0Ah BYTE (returned) device type
01h streamer
---request 02h---
08h BYTE target ID
09h BYTE logical unit number
0Ah DWORD data allocation length
0Eh BYTE sense allocation length
0Fh DWORD data buffer pointer
13h DWORD next request pointer (for linking)
17h BYTE CDB length
18h BYTE (returned) host adapter status
11h select timeout
12h data overrun
13h bus error
14h bus failure
19h BYTE (returned) target status
02h sense data stored in SRB
08h target busy
18h reservation error
1Ah DWORD post routine address
1Eh WORD real mode Post DS
20h DWORD SRB pointer
24h WORD reserved
26h DWORD SRB physical address
2Ah 22 BYTEs SCSIMGR$ workspace
40h N BYTEs CCB (20-24 bytes)
---request 04h---
08h BYTE target ID
09h BYTE logical unit number
0Ah 14 BYTEs reserved
18h BYTE (returned) host adapter status (see above)
19h BYTE (returned) target status (see above)
1Ah DWORD post routine address
1Eh 34 BYTEs workspace
Format of CCB:
Offset Size Description
00h BYTE command code
01h rewind
05h get block size limits
08h read
0Ah write
10h write file marks
11h SCSI Space (set position?)
12h SCSI Inquire
19h erase
1Bh load/unload media
01h BYTE flags
bits 4-0: vary by function
bits 7-5: logical unit number
02h BYTE "adr_1"
03h BYTE "adr_0"
04h BYTE length
05h BYTE control
...
06h/0Ah 14 BYTEs buffer for sense data
----------214402-----------------------------
INT 21 U - Qualitas 386MAX v6.00+ - IOCTL INPUT - GET STATE
AX = 4402h
BX = file handle for device "386MAX$$"
CX = 005Ah
DS:DX -> 386MAX state buffer (see below)
Return: CF clear if successful
buffer filled
AX = number of bytes actually copied
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes: the buffer must be one byte larger than the value given in CX; if the
value is less than 5Ah, only a partial state record will be returned
the state is 40h bytes for 386MAX (actually ASTEMM) v2.20 ("386MAX$$"
did not exist yet, use "QMMXXXX0" and then "EMMXXXX0" instead) and
56h bytes for v5.11.
to invoke 386MAX API functions, push DX onto the stack, load DX with
the word at offset 25h in the returned state, load all other
registers as needed for the desired function, and execute an
OUT DX,AL or OUT DX,AX; DX will be set to the pushed value on return
if it is not otherwise modified by the API function.
SeeAlso: AX=4403h"386MAX",INT 67/AH=3Fh
Format of 386MAX v6.01 state:
Offset Size Description
00h BYTE version number of state structure (must be set on entry;
v6.01 returns an error if not 03h)
01h 6 BYTEs signature "386MAX"
07h 4 BYTEs version string "N;NN" (i.e. "6;01" for v6.01)
0Bh WORD segment of low-memory portion of 386MAX.SYS
0Dh 2 BYTEs ???
0Fh WORD segment of ??? memory block or 0000h
11h WORD bit flags
bit 1: ???
bit 2: ???
bit 3: ??? (cleared by calling INT 67 functions)
bit 5: ???
bit 6: 386MAX active???
bit 7: 386MAX is providing EMS services
bit 8: ???
bit 9: ??? (see INT 15/AX=2402h)
bit 10: ???
bit 11: ???
bit 12: ???
bit 13: QPMS has been used
bit 14: ???
bit 15: ???
13h WORD starting address of video memory in K
15h 8 BYTEs ???
1Dh WORD KBytes extended memory used by 386MAX
1Fh 2 BYTEs ???
21h WORD ???
23h WORD IO port to write (OUT DX,AL) to invoke 386MAX INT 15 functions
25h WORD IO port to write (OUT DX,AL) to invoke 386MAX API functions
27h WORD ???
29h 2 BYTEs ???
2Bh DWORD ???
2Fh 4 BYTEs ???
33h WORD system configuration??? flags
bit 1: ROM compressed???
bit 3: ???
bit 5: 386MAX loaded into high memory
bit 11: PC/XT (thus only single 8259 interrupt controller
present, DMA only in 1st megabyte, etc)
35h WORD ??? bit flags
37h 4 BYTEs ???
3Bh WORD segment of first MCB in high memory chain???
3Dh WORD flags
bit 2: no DPMI services
bit 11: don't backfill holes in video memory area
bit 12: don't backfill below video memory???
3Fh WORD flags
bit 7: ???
41h WORD flags
bit 0: Windows3 support enabled
bit 8: ???
43h 2 BYTEs ???
45h WORD amount of memory to report available on INT 15/AH=88h
47h 4 BYTEs ???
4Bh WORD ???
4Dh 2 BYTEs ???
4Fh WORD ???
51h WORD bit flags
bit 12: ???
53h DWORD old INT 21h
57h DWORD pointer to 386MAX's EMS (INT 67h) handler
Format of high memory info record:
Offset Size Description
00h WORD segment address of memory region
02h WORD size of memory region in paragraphs
04h BYTE type or flags???
00h if locked out
02h if EMS page frame
04h if high RAM
42h if ROM
05h BYTE ???
Format of ROM shadowing record:
Offset Size Description
00h WORD segment of ROM???
02h WORD segment of ROM???
04h 2 BYTEs ???
06h WORD size of shadowed ROM in paragraphs
08h 4 BYTEs ???
Values for memory type:
00h unused by EMS
01h DOS
04h page frame overlapping ROM???
80h high memory
84h page frame???
87h video ROM???
Note: the type may be 00h (unused) if the 16K page is split among different
uses (such as ROM and high RAM)
Call 386MAX API (via OUT DX,AL) with:
STACK: WORD value for DX
AH = 01h get high memory information
ES:DI -> buffer for array of high memory info records
(see above)
Return: CX = number of records placed in buffer
AH = 02h get shadowed ROM info???
ES:DI -> buffer for array of ROM shadowing records (see above)
Return: CX = number of records placed in buffer
AH = 03h get 386MAX state
ES:DI -> 90-byte buffer for state (see above)
Return: AH = 00h (successful)
buffer filled
Note: unlike INT 21/AX=4402h"386MAX", this function omits
the first byte specifying the state buffer version
AH = 04h get memory types???
ES:DI -> buffer for memory type info (array of bytes, one per
16K page) (see above)
Return: CX = number of bytes placed in buffer
AH = 05h get ???
AL = subfunction
00h invoke INT 15/AX=2401h first
01h don't invoke INT 15/AX=2401h first
CX = number of bytes to copy (0000h for default)
SI = ???
ES:DI -> buffer for ???
Return: CX = number of bytes actually copied
???
AH = 06h get memory speed info
ES:DI -> buffer for memory speed records (see below)
Return: AH = 00h (successful)
CX = number of bytes placed in buffer
Note: this function can take over a second to execute
AH = 07h ???
???
Return: ???
AH = 08h ???
AL = ??? (00h or nonzero)
AH = 09h toggle ??? flags
BX = bitmask of bits of ??? flags (word at state+11h) to toggle
Return: AH = 00h (successful)
Note: invokes INT 15/AX=2401h first
AH = 0Ah toggle ??? flags
BX = bitmask of bits of ??? (word at state+33h) to toggle
Return: AH = 00h (successful)
Notes: invokes INT 15/AX=2401h first
does ??? if bit 3 on after specified bits are toggled
AH = 0Bh toggle ??? flags
BX = bitmask of bits of ??? (word at state+35h) to toggle
Return: AH = 00h (successful)
Note: invokes INT 15/AX=2401h first
AH = 0Ch toggle ??? flags
BX = bitmask of bits of ??? (word at state+41h) to toggle
Return: AH = 00h (successful)
Note: invokes INT 15/AX=2401h first
AH = 0Dh specify 386MAX high-memory location
BX = segment address of high-memory real-mode portion of 386MAX
???
Return: AH = status (00h successful)
???
AH = 0Eh CRT controller register virtualization
AL = subfunction
00h allow access to CRTC I/O ports 03B4h/03B5h, 03D4h/03D5h
01h trap accesses to CRTC I/O ports
AH = 0Fh reboot system
Return: never
AH = 11h get high memory information
ES:DI -> 96-byte buffer for high memory info
Return: AH = 00h (successful)
ES:DI buffer filled
Notes: each byte in buffer contains bit flags for a 4K page in
the A000h-FFFFh region
bit 0: ???
bit 1: physical address same as linear address
bit 2: EMS page frame
bit 6: ???
this function can take over a second to execute
AH = 12h ???
AL = subfunction
00h ???
01h ???
???
Return: AH = 00h (successful) if AL=00h or 01h
AH = 8Fh otherwise
AH = 13h page protection???
AL = subfunction
00h set all ??? 4K pages to read-only???
01h set all ??? 4K pages to read-write???
???
Return: AH = 00h (successful) if AL=00h or 01h
AH = 8Fh otherwise
AH = 15h ???
???
Return: ???
AH = 16h get 386MAX memory usage screen
ES:DI -> buffer for memory info display
CX = size of buffer in bytes
Return: ES:DI buffer filled with '$'-terminated string (if
large enough to hold entire usage screen)
AH = 17h Windows 3 startup/termination
AL = subfunction
00h Windows3 initializing
DX (on stack) = Windows startup flags
DI = Windows version number (major in upper byte)
ES:BX = 0000h:0000h
DS:SI = 0000h:0000h
Return: CX = 0000h if OK for Windows to load
<> 0 if Windows should not load
ES:BX -> startup info structure
DS:SI -> Virtual86 mode enable/disable callback
01h Windows3 terminating
ES:BX -> ???
DX (on stack) = Windows exit flags
Return: ???
AH = 18h QPMS (Qualitas Protected Memory Services)
AL = subfunction
00h get QPMS configuration
Return: BX = starting segment of QPMS memory window
CX = number of 4K pages reserved for QPMS???
DX = number of 4K pages in QPMS window???
01h map QPMS memory page???
BX = 4K page number within memory reserved for QPMS???
CL = 4K page number within QPMS memory window???
02h mark all QPMS memory read-only
03h mark all QPMS memory read-write
Return: AH = status (00h,8Ah,8Bh,8Fh)
AH = 19h get linear address for physical address
EDX = physical address (low word on stack)
Return: AH = status
00h successful
EDX = linear address at which physical address
may be accessed
8Bh physical address currently not addressable
Note: calls INT 15/AX=2401h first
AH = 1Ah set page table entry???
EDX = new page table entry??? (low word on stack)
ESI = linear address of page???
Return: AH = status (00h,8Bh)
Note: calls INT 15/AX=2401h first
AH = 1Bh get ???
Return: AH = status
BX = ???
CX = ???
EDX = physical address of ???
AH = 1Ch get original interrupt vector
AL = interrupt vector (00h-7Fh)
Return: AH = 00h (successful)
EDX = original vector before 386MAX loaded (segment in
high word, offset in low word)
Note: no range checking is performed; requests for INTs 80h-
FFh will return random values
AH = 1Dh display string???
SI = ???
Return: AH = 00h (successful)
???
AH = 1Eh ???
ES:DI -> ???
???
Return: ???
AH = 1Fh ???
???
Return: AX = 0000h if successful
BX = ??? (0001h for 386MAX v6.01)
CL = ???
DL = ??? (5Ah for 386MAX v6.01)
DH = ??? (00h for 386MAX v6.01)
SI = ???
ES???:DI -> ???
AH = 40h-5Dh EMS services (see INT 67/AH=40h etc)
AH = DEh VCPI services (see INT 67/AX=DE00h etc)
Return: AH = status (as for EMS INT 67 calls)
00h successful
80h internal error
81h hardware malfunction
83h invalid handle
84h undefined function
8Ah invalid logical page nuber
8Bh illegal physical page number
8Fh undefined subfunction
A4h access denied
etc.
STACK popped (value placed in DX if no specific return value for DX)
Format of memory speed record:
Offset Size Description
00h DWORD page table entry for 4K page
04h WORD number of microticks (840ns units) required for REP LODSD of
entire 4K page
----------214402-----------------------------
INT 21 - PGS1600.DEV - IOCTL - GET CONFIGURATION INFO
AX = 4402h
BX = file handle for device "PGS1600$"
CX = 0018h (size of buffer)
DS:DX -> configuration buffer (see below)
Return: CF clear if successful
buffer filled
AX = number of bytes actually copied
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: PGS1600.DEV is a device driver for the Cornerstone Technology PG1600
display adapter, which provides a 1600x1200 monochrome display as
well as one of two emulations, MDA or CGA.
SeeAlso: AX=4403h"PGS1600"
Format of configuration information:
Offset Size Description
00h WORD version (high byte = major, low byte = minor)
02h WORD board initialisation mode
04h WORD board I/O address
03D0h CGA emulation
03B0h MDA emulation
0390h no emulation
0350h no emulation, alternate
06h WORD emulation buffer segment
B800h CGA emulation
B000h MDA emulation
0000h no emulation
08h WORD PG1600 graphics buffer segment
0Ah WORD number of bytes between consecutive graphic rows
0Ch WORD horizontal pixel size
0Eh WORD vertical pixel size
10h WORD horizontal dots per inch
12h WORD vertical dots per inch
14h WORD graphics buffer bits per pixel
16h WORD monitor bits per pixel
----------214402-----------------------------
INT 21 - PC/TCP IPCUST.SYS - RESET CONFIGURATION DATA READ POINTER
AX = 4402h
BX = file handle referencing device "$IPCUST"
CX, DS:DX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: there are a total of 378h bytes of configuration data for IPCUST.SYS
version 2.05. If less than the entire data is read or written,
the next read/write continues where the previous one ended; this
call and AX=4403h both reset the location at which the next
operation starts to zero
SeeAlso: AH=3Fh"IPCUST",AH=40h"IPCUST",AX=4403h"IPCUST"
----------214403-----------------------------
INT 21 - DOS 2+ - IOCTL - WRITE TO CHARACTER DEVICE CONTROL CHANNEL
AX = 4403h
BX = file handle referencing character device
CX = number of bytes to write
DS:DX -> data to write
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Notes: format of data is driver-specific (see below for some specific cases)
if the file handle refers to "4DOSSTAK", the 4DOS (v2.x-3.03)
KEYSTACK.SYS driver will push the specified characters on the
keyboard stack; similarly for "NDOSSTAK", the NDOS KEYSTACK.SYS
driver will push the characters onto the keyboard stack
SeeAlso: AX=4400h,AX=4402h,AX=4405h,INT 2F/AX=122Bh,INT 2F/AX=D44Dh
SeeAlso: INT 2F/AX=D44Fh
----------214403-----------------------------
INT 21 - SMARTDRV.SYS - IOCTL - CACHE CONTROL
AX = 4403h
BX = handle for device "SMARTAAR"
CX = number of bytes to write
DS:DX -> SMARTDRV control block (see below)
Return: CF clear if successful
AX = number of bytes actually written
= 0000h if control block too small for given command
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"SMARTDRV",INT 2F/AX=4A10h
Format of SMARTDRV control block:
Offset Size Description
00h BYTE function code
00h flush cache
01h flush and discard cache
02h disable caching (flushes and discards cache first)
03h enable caching
04h control write caching
05h set flushing tick count
06h lock cache contents
07h unlock cache contents
08h set flush-on-reboot flag
09h unused
0Ah control full-track caching
0Bh reduce cache size
0Ch increase cache size
0Dh set INT 13 chain address
---function 04h---
01h BYTE write caching control action
00h turn off write-through
01h turn on write-through
02h turn off write buffering (also flushes cache)
03h turn on write buffering (also flushes cache)
---function 05h---
01h WORD number of timer ticks between cache flushes
---function 08h---
01h BYTE new flush-on-reboot flag (00h off, 01h on)
---function 0Ah---
01h BYTE full-track writes are
00h not cached
01h cached
---functions 0Bh,0Ch---
01h WORD number of 16K pages by which to increase/reduce cache size
---function 0Dh---
01h DWORD new address to which to chain on INT 13
Note: the previous address is not preserved
----------214403-----------------------------
INT 21 - CD-ROM device driver - IOCTL OUTPUT
AX = 4403h
BX = file handle referencing character device for CD-ROM driver
CX = number of bytes to write
DS:DX -> control block (see below)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4402h"CD-ROM",INT 2F/AX=0802h
Format of control block:
Offset Size Description
00h BYTE function code
00h eject disk
01h lock/unlock door
02h reset drive
03h control audio channel
04h write device control string
05h close tray
---functions 00h,02h,05h---
no further fields
---function 01h---
01h BYTE lock function
00h unlock door
01h lock door
---function 03h---
01h BYTE input channel (0-3) for output channel 0
02h BYTE volume for output channel 0
03h BYTE input channel (0-3) for output channel 1
04h BYTE volume for output channel 1
05h BYTE input channel (0-3) for output channel 2
06h BYTE volume for output channel 2
07h BYTE input channel (0-3) for output channel 3
08h BYTE volume for output channel 3
Note: output channels 0 and 1 are left and right, 2 and 3 are left prime and
right prime; a volume of 00h is off
---function 04h---
01h N BYTEs bytes to send directly to the CD-ROM drive without
interpretation
----------214403-----------------------------
INT 21 - Brian Antoine Seagate ST-01 SCSI.SYS - IOCTL - EXECUTE COMMANDS
AX = 4403h
BX = handle for device "SCSITAPE"
CX = number of bytes to write
DS:DX -> SCSITAPE control block (see below)
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4405h"ST-01",INT 78/AH=10h
Format of SCSITAPE control block:
Offset Size Description
00h WORD command type
'F' Format (argument 1 = interleave, argument 2 = format type)
'E' Erase
'R' Rewind
'L' Load
'N' No Load
'S' Space (argument 1 = count, argument 2 = type)
'M' File Mark (argument 1 = count)
'A' Reassign
02h WORD argument 1
04h WORD argument 2
06h WORD segment of command buffer
08h WORD offset of command buffer
0Ah WORD length of command buffer
----------214403-----------------------------
INT 21 U - AI Architects - OS/x86??? - API
AX = 4403h
BX = handle for device "AIA_OS"
CX = number of bytes to write (ignored)
DS:DX -> 12-byte buffer, first byte is command:
81h installation check
82h get API entry point
84h uninstall
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Ch,0Dh) (see AH=59h)
Notes: these functions are only available if the DOS extender was loaded as a
device driver in CONFIG.SYS
called by TKERNEL (a licensed version of AI Architects/Ergo OS/x86)
SeeAlso: INT 2F/AX=FBA1h/BX=0081h,INT 2F/AX=FBA1h/BX=0082h
Format of buffer on return:
Offset Size Description
00h 4 BYTEs signature "IABH"
---if func 81h---
(no additional fields)
---if func 82h---
04h DWORD pointer to API entry point (see INT 2F/AX=FBA1h/BX=0082h)
---if func 84h---
04h WORD success indicator
06h WORD segment of ???
08h WORD segment of ??? memory block to free if nonzero
0Ah WORD segment of ??? memory block to free if nonzero
----------214403-----------------------------
INT 21 U - Qualitas 386MAX v6.01 - SET STATE
AX = 4403h
BX = handle for device "386MAX$$"
CX = number of bytes to copy (up to 5Ah)
DS:DX -> 386MAX state buffer (see AX=4402h"386MAX")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: the first byte of the buffer must be either 01h, 02h, or 03h
(specifying the version of the state record) and the buffer must
contain CX bytes AFTER the initial byte
SeeAlso: AX=4402h"386MAX"
----------214403-----------------------------
INT 21 - PGS1600.DEV - IOCTL - SET CONFIGURATION???
AX = 4403h
BX = file handle for device "PGS1600$"
CX = 0018h (size of buffer)
DS:DX -> configuration buffer (see AX=4402h"PGS1600")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: PGS1600.DEV is a device driver for the Cornerstone Technology PG1600
display adapter, which provides a 1600x1200 monochrome display as
well as one of two emulations, MDA or CGA.
SeeAlso: AX=4402h"PGS1600"
----------214403-----------------------------
INT 21 - PC/TCP IPCUST.SYS - RESET CONFIGURATION DATA READ POINTER
AX = 4403h
BX = file handle referencing device "$IPCUST"
CX, DS:DX ignored
Return: CF clear if successful
AX destroyed
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: there are a total of 378h bytes of configuration data for IPCUST.SYS
version 2.05. If less than the entire data is read or written,
the next read/write continues where the previous one ended; this
call and AX=4402h both reset the location at which the next
operation starts to zero
SeeAlso: AH=3Fh"IPCUST",AH=40h"IPCUST",AX=4402h"IPCUST"
----------214404-----------------------------
INT 21 - DOS 2+ - IOCTL - READ FROM BLOCK DEVICE CONTROL CHANNEL
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to read
DS:DX -> buffer
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: format of data is driver-specific
SeeAlso: AX=4402h,AX=4405h,INT 2F/AX=122Bh
----------214404-----------------------------
INT 21 - Stacker - GET DEVICE DRIVER ADDRESS AND SET VOLUME NUMBER
AX = 4404h
BL = drive number (00h = default, 01h = A:, etc)
CX = 0004h
DS:DX -> DWORD buffer to receive device driver address
Note: In addition to returning the address of the Stacker device driver,
this call also sets the volume number at offset 3Eh in the device
driver (see INT 25/AX=CDCDh)
SeeAlso: INT 25/AX=CDCDh
----------214404-----------------------------
INT 21 - Stacker - GET STACVOL FILE SECTORS
AX = 4404h
BL = drive number (0 is current drive)
CX = byte count (i.e., 200h = 1 sector)
DS:DX -> buffer (see below)
Return: Data Buffer contains the number of sectors requested from the
STACVOL physical file for the drive specified.
Format of stacker buffer:
Offset Size Description
00h WORD 01CDh
02h WORD sector count
04h DWORD number of starting sector
08h DWORD far pointer to Data Buffer
----------214405-----------------------------
INT 21 - DOS 2+ - IOCTL - WRITE TO BLOCK DEVICE CONTROL CHANNEL
AX = 4405h
BL = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to write
DS:DX -> data to write
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: format of data is driver-specific
SeeAlso: AX=4403h,AX=4404h,INT 2F/AX=122Bh
----------214405-----------------------------
INT 21 - Brian Antoine Seagate ST-01 SCSI.SYS - IOCTL - EXECUTE COMMANDS
AX = 4405h
BX = drive number (00h = default, 01h = A:, etc)
CX = number of bytes to write
DS:DX -> SCSIDISK control block (see AX=4403h"ST-01")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
SeeAlso: AX=4403h"ST-01"
----------214406-----------------------------
INT 21 - DOS 2+ - IOCTL - GET INPUT STATUS
AX = 4406h
BX = file handle
Return: CF clear if successful
AL = input status
00h not ready (device) or at EOF (file)
FFh ready
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: files may not register as being at EOF if positioned there by AH=42h
SeeAlso: AX=4407h,INT 2F/AX=122Bh
----------214407-----------------------------
INT 21 - DOS 2+ - IOCTL - GET OUTPUT STATUS
AX = 4407h
BX = file handle
Return: CF clear if successful
AL = input status
00h not ready
FFh ready
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note: for DOS 2+, files are always ready for output, even if the disk is
full or no media is in the drive
SeeAlso: AX=4406h,INT 2F/AX=122Bh
----------214408-----------------------------
INT 21 - DOS 3.0+ - IOCTL - CHECK IF BLOCK DEVICE REMOVABLE
AX = 4408h
BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
AX = 0000h if removable
= 0001h if fixed
CF set on error
AX = error code (01h,0Fh) (see AH=59h)
SeeAlso: AX=4400h,AX=4409h,INT 2F/AX=122Bh
----------214409-----------------------------
INT 21 - DOS 3.1+ - IOCTL - CHECK IF BLOCK DEVICE REMOTE
AX = 4409h
BL = drive number (00h = default, 01h = A:, etc)
Return: CF clear if successful
DX = device attribute word
bit 15: drive is SUBSTituted
bit 12: drive is remote
bit 9: direct I/O not allowed
CF set on error
AX = error code (01h,0Fh) (see AH=59h)
Note: on local drives, DX bits not listed above are the attribute word from
the device driver header (see AH=52h); for remote drives, the other
bits appear to be undefined
SeeAlso: AX=4400h,AX=4408h,AX=440Ah,INT 2F/AX=122Bh
----------21440A-----------------------------
INT 21 - DOS 3.1+ - IOCTL - CHECK IF HANDLE IS REMOTE
AX = 440Ah
BX = handle
Return: CF clear if successful
DX = attribute word (as stored in SFT)
bit 15: set if remote
bit 14: date/time not set on close
CF set on error
AX = error code (01h,06h) (see AH=59h)
Note: if file is remote, Novell Advanced NetWare 2.0 returns the number of
the file server on which the handle is located in CX
SeeAlso: AX=4400h,AX=4409h,AH=52h,INT 2F/AX=122Bh
----------21440B-----------------------------
INT 21 - DOS 3.1+ - IOCTL - SET SHARING RETRY COUNT
AX = 440Bh
CX = pause between retries (default 1)
DX = number of retries (default 3)
Return: CF clear if successful
CF set on error
AX = error code (01h) (see AH=59h)
Notes: delay is dependent on processor speed (value in CX specifies number of
64K-iteration empty loops to execute)
if DX=0000h on entry, the retry count is left unchanged
SeeAlso: AH=52h,INT 2F/AX=1224h,INT 2F/AX=122Bh
----------21440C-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GENERIC CHARACTER DEVICE REQUEST
AX = 440Ch
BX = device handle
CH = category code
00h unknown (DOS 3.3+)
01h COMn: (DOS 3.3+)
03h CON (DOS 3.3+)
05h LPTn:
9Eh Media Access Control driver (STARLITE)
00h-7Fh reserved for Microsoft
80h-FFh reserved for OEM/user-defined
CL = function
00h MAC driver Bind (STARLITE)
45h set iteration count
4Ah select code page
4Ch start code-page preparation
4Dh end code-page preparation
5Fh set display information (DOS 4.0)
65h get iteration count
6Ah query selected code page
6Bh query prepare list
7Fh get display information (DOS 4.0)
DS:DX -> (DOS) parameter block (see below)
SI = parameter to pass to driver (European MSDOS 4.0, OS/2 comp box)
DI = parameter to pass to driver (European MSDOS 4.0, OS/2 comp box)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
DS:DX -> iteration count if CL=65h
SI = returned value (European MSDOS 4.0, OS/2 comp box)
DI = returned value (European MSDOS 4.0, OS/2 comp box)
DS:DX -> (OS/2 comp box) data block
Note: bit assignments for function code in CL:
bit 7: set to ignore if unsupported, clear to return error
bit 6: set if passed to driver, clear if intercepted by DOS
bit 5: set if queries data from device, clear if sends command
bits 4-0: subfunction
SeeAlso: AX=440Dh,INT 2F/AX=0802h,INT 2F/AX=122Bh,INT 2F/AX=1A01h
Format of parameter block for function 00h:
Offset Size Description
00h 8 BYTEs ASCIZ signature "STARMAC"
08h WORD version
0Ah WORD flags
bit 0: media requires connect or listen request before use
bit 1: network is a LAN (broadcast/multicast supported)
bit 2: point-to-point network
0Ch WORD handle for use with MAC driver's private interface (filled in
by MAC driver)
0Eh WORD context
10h WORD approximate speed in KB/sec (filled in by MAC driver)
12h WORD approximate cost in cents per hour (filled in by MAC driver)
14h WORD maximum packet size in bytes (filled in by MAC driver)
16h WORD addressing format (filled in by MAC driver)
0000h general addressing
0001h Ethernet addressing
0002h Token Ring addressing
0003h Token Bus addressing
18h DWORD Send entry point (filled in by MAC driver)
1Ch DWORD RegisterEventHandler entry point (filled in by MAC driver)
20h DWORD SetPacketFilter entry point (filled in by MAC driver)
24h DWORD UnBind entry point (filled in by MAC driver)
Format of parameter block for function 45h:
Offset Size Description
00h WORD number of times output is attempted before driver assumes
device is busy
Format of parameter block for functions 4Ah and 6Ah:
Offset Size Description
00h WORD length of data
02h WORD code page ID
04h 2N BYTEs DCBS (double byte character set) lead byte range
start/end for each of N ranges (DOS 4.0)
WORD 0000h end of data (DOS 4.0)
Format of parameter block for function 4Dh:
Offset Size Description
00h WORD length of data
02h WORD code page ID
Format of parameter block for function 4Ch:
Offset Size Description
00h WORD flags
DISPLAY.SYS = 0000h
PRINTER.SYS bit 0 clear to prepare downloaded font, set to
prepare cartridge selection
02h WORD length of remainder of parameter block
04h WORD number of code pages following
06h N WORDs code page 1,...,N
Format of parameter block for functions 5Fh and 7Fh:
Offset Size Description
00h BYTE level (0 for DOS 4.x and 5.0)
01h BYTE reserved (0)
02h WORD length of following data (14)
04h WORD control flags
bit 0 set for blink, clear for intensity
bits 1 to 15 reserved
06h BYTE mode type (1=text, 2=graphics)
07h BYTE reserved (0)
08h WORD colors
0 = monochrome
else N bits per pixel
0Ah WORD pixel columns
0Ch WORD pixel rows
0Eh WORD character columns
10h WORD character rows
Format of parameter block for function 6Bh:
Offset Size Description
00h WORD length of following data
02h WORD number of hardware code pages
04h N WORDs hardware code pages 1,...,N
WORD number of prepared code pages
N WORDs prepared code pages 1,...,N
----------21440C-----------------------------
INT 21 - Greg Shenaut ASPITAPE.SYS - INTERFACE
AX = 440Ch
BX = device handle
CH = category code
07h tape (ASPITAPE.SYS)
CL = function
01h "mtop" - perform tape operation
02h "mtget" - get tape status
03h ignore end-of-tape errors
04h enable end-of-tape errors
DS:DX -> parameter block (see below)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
DS:DX -> data block
Notes: This device driver is a simple DOS interface to the Adaptec Advanced
SCSI Programming Interface (ASPI). It provides the following device
names as access to the SCSI tape, 'RMTx' (rewind on close) and
'NRMTx' (NO rewind on close) where x can go from 0 to 3. There may
also be the following names 'MTx' and 'NMTx' which default to 1024
byte blocks. The names may also have a '$' appended to try and make
them unique from file names of 'RMT0' etc.
once opend these devices must be put into RAW mode
SeeAlso: AX=4402h"ASPI"
Format of mtop parameter block:
Offset Size Description
00h WORD operation code
00h "MTWEOF" - write an end-of-file record
01h "MTFSF" - forward space file
02h "MTBSF" - backward space file
03h "MTFSR" - forward space record
04h "MTBSR" - backward space record
05h "MTREW" - rewind
06h "MTOFFL" - rewind and unload
07h "MTNOP" - perform TEST UNIT READY
02h DWORD repetition count
Format of mtget parameter block:
Offset Size Description
00h BYTE ASPI host ID
01h BYTE SCSI target ID
02h BYTE SCSI logical unit number
03h BYTE device parameters
bit 0: drive must use fixed-block read and write
bit 7: drive is an ASPI device
04h BYTE current device state
bit 0: device currently opened in buffered mode
bit 1: drive currently opened in nonbuffered mode
bit 2: rewind drive on last close
bit 3: drive has been written on
bit 4: drive has been read from
bit 5: next read will return 0 bytes
bit 6: EOM will resemble EOF
bit 7: drive may be busy rewinding
05h BYTE unit number within driver
06h WORD fixed block blocksize
08h BYTE last SCSI status
09h BYTE last SCSI sense key
0Ah WORD last SCSI opcode (packed)
bits 0-7: SCSI operation (SCSI packet byte 0)
bits 8-10: SCSI flags (SCSI packet byte 1)
bits 11-12: ASPI "Direction Bits" (ASPI SRB byte 3)
0Ch WORD residual bytes from SCSI opcode
----------21440D-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GENERIC BLOCK DEVICE REQUEST
AX = 440Dh
BL = drive number (00h=default,01h=A:,etc)
CH = category code
08h disk drive
00h-7Fh reserved for Microsoft
80h-FFh reserved for OEM/user-defined
CL = function
40h set device parameters
41h write logical device track
42h format and verify logical device track
46h (DOS 4+) set volume serial number (see also AH=69h)
47h (DOS 4+) set access flag
60h get device parameters
61h read logical device track
62h verify logical device track
66h (DOS 4+) get volume serial number (see also AH=69h)
67h (DOS 4+) get access flag
68h (DOS 5+) sense media type
DS:DX -> (DOS) parameter block (see below)
SI:DI -> (OS/2 comp box) parameter block (see below)
Return: CF set on error
AX = error code (01h,02h) (see AH=59h)
CF clear if successful
DS:DX -> data block if CL=60h or CL=61h
Notes: DOS 4.01 seems to ignore the high byte of the number of directory
entries in the BPB for diskettes.
functions 46h and 66h undocumented in DOS 4.x, documented for DOS 5.0
SeeAlso: AX=440Ch,AH=69h,INT 2F/AX=0802h,INT 2F/AX=122Bh
Format of parameter block for functions 40h, 60h:
Offset Size Description
00h BYTE special functions
bit 0 set if function to use current BPB, clear if Device
BIOS Parameter Block field contains new default BPB
bit 1 set if function to use track layout fields only
must be clear if CL=60h
bit 2 set if all sectors in track same size (should be set)
bits 3-7 reserved
01h BYTE device type
00h 320K/360K disk
01h 1.2M disk
02h 720K disk
03h single-density 8-inch disk
04h double-density 8-inch disk
05h fixed disk
06h tape drive
07h (DOS 3.3+) 1.44M floppy
08h read/write optical disk
09h (DOS 5.0) 2.88M floppy
0Ah other type of block device
02h WORD device attributes
bit 0 set if nonremovable medium
bit 1 set if door lock ("changeline") supported
bits 2-15 reserved
04h WORD number of cylinders
06h BYTE media type
for 1.2M drive
00h 1.2M disk (default)
01h 320K/360K disk
always 00h for other drive types
07h 31 BYTEs device BPB (see AH=53h), bytes after BPB offset 1Eh omitted
26h WORD number of sectors per track (start of track layout field)
not used by function 60h
28h N word pairs: number,size of each sector in track
Format of parameter block for functions 41h, 61h:
Offset Size Description
00h BYTE special functions (reserved, must be zero)
01h WORD number of disk head
03h WORD number of disk cylinder
05h WORD number of first sector to read/write
07h WORD number of sectors
09h DWORD transfer address
Format of parameter block for functions 42h, 62h:
Offset Size Description
00h BYTE reserved, must be zero (DOS <3.2)
bit 0=0: format/verify track
1: format status call (DOS 3.2+)
bits 1-7 reserved, must be zero
on return (DOS 4.x):
bit 0: set if specified tracks, sectors/track supported
bit 1: set if function not supported by BIOS
bit 2: set if specified tracks, sectors/track not supported
bit 3: set if no disk in drive
01h WORD number of disk head
03h WORD number of disk cylinder
Format of parameter block for functions 46h, 66h:
Offset Size Description
00h WORD info level (00h)
02h DWORD disk serial number (binary)
06h 11 BYTEs volume label or "NO NAME "
11h 8 BYTEs filesystem type "FAT12 " or "FAT16 " (CL=66h only)
Format of parameter block for functions 47h, 67h:
Offset Size Description
00h BYTE special-function field (must be zero)
01h BYTE disk-access flag, nonzero if access allowed by driver
Format of parameter block for function 68h:
Offset Size Description
00h BYTE 01h for default media type, 00h for any other media type
01h BYTE 02h for 720K, 07h for 1.44M, 09h for 2.88M
----------21440E-----------------------------
INT 21 - DOS 3.2+ - IOCTL - GET LOGICAL DRIVE MAP
AX = 440Eh
BL = drive number (00h=default,01h=A:,etc)
Return: CF set on error
AX = error code (01h,0Fh) (see AH=59h)
CF clear if successful
AL = 00h block device has only one logical drive assigned
1..26 the last letter used to reference the drive (1=A:,etc)
SeeAlso: AX=440Fh,INT 2F/AX=122Bh
----------21440F-----------------------------
INT 21 - DOS 3.2+ - IOCTL - SET LOGICAL DRIVE MAP
AX = 440Fh
BL = physical drive number (00h=default,01h=A:,etc))
Return: CF set on error
AX = error code (01h,0Fh) (see AH=59h)
CF clear if successful
drive now responds to next logical drive number
Note: maps logical drives to physical drives, similar to DOS's treatment of
a single physical floppy drive as both A: and B:
SeeAlso: AX=440Eh,INT 2F/AX=122Bh
----------214410-----------------------------
INT 21 - DOS 5.0 - IOCTL - QUERY GENERIC IOCTL CAPABILITY (HANDLE)
AX = 4410h
BX = handle for device
CH = category code (see AX=440Ch)
CL = function code
Return: CF clear if successful
AX = 0000h specified IOCTL function is supported
CF set on error
AL = 01h IOCTL capability not available
Note: a program which wishes to use Generic IOCTL calls beyond those in the
standard DOS 3.2 set may use this call first to see whether a
particular call is supported
SeeAlso: AX=440Ch,AX=440Dh,AX=4411h
----------214410BXFFFF-----------------------
INT 21 U - NewSpace - ENABLE DRIVER
AX = 4410h
BX = FFFFh
Notes: NewSpace is a TSR by Isogon Corporation which automatically compresses
all files as they are written and decompresses them as they are read
compressed files are not accessible unless the driver is enabled
SeeAlso: AX=4411h/BX=FFFFh
----------214411-----------------------------
INT 21 - DOS 5.0 - IOCTL - QUERY GENERIC IOCTL CAPABILITY (DRIVE)
AX = 4411h
BL = drive number
CH = category code (see AX=440Dh)
CL = function code
Return: CF clear if successful
AX = 0000h specified IOCTL function is supported
CF set on error
AL = 01h IOCTL capability not available
Note: a program which wishes to use Generic IOCTL calls beyond those in the
standard DOS 3.2 set may use this call first to see whether a
particular call is supported
SeeAlso: AX=440Ch,AX=440Dh,AX=4410h
----------214411BXFFFF-----------------------
INT 21 U - NewSpace - DISABLE DRIVER
AX = 4411h
BX = FFFFh
Notes: NewSpace is a TSR by Isogon Corporation which automatically compresses
all files as they are written and decompresses them as they are read
compressed files are not accessible unless the driver is enabled
SeeAlso: AX=4410h/BX=FFFFh
----------214412-----------------------------
INT 21 - DR-DOS 5+ - DETERMINE DOS TYPE
AX = 4412h
CF set
Return: CF set if not DR-DOS
AX = error code (see AH=59h)
CF clear if DR-DOS
DX = AX = version code
1060h = ???
1063h = DR-DOS 3.41 ???
1065h = DR-DOS 5.0
1067h = DR-DOS 6.0
Note: this call is identical to AX=4452h
SeeAlso: AX=4452h
----------214412BXFFFF-----------------------
INT 21 U - NewSpace - INSTALLATION CHECK???
AX = 4412h
BX = FFFFh
Return: AX = PSP segment of NewRes (resident driver for NewSpace)
BX:DX -> ???
CX = ???
SeeAlso: AX=4411h/BX=FFFFh
----------214413BXFFFF-----------------------
INT 21 U - NewSpace - GET ???
AX = 4413h
BX = FFFFh
Return: AX = code segment of NewRes (resident driver for NewSpace)
BX = offset of ???
SeeAlso: AX=4412h/BX=FFFFh
----------214414-----------------------------
INT 21 U - DR-DOS 5.0 - SET GLOBAL PASSWORD
AX = 4414h
DS:DX -> password string (blank-padded to 8 characters)
Desc: Specify the master password for accessing files.
Note: this call is identical to AX=4454h
SeeAlso: AX=4454h
----------214414BXFFFF-----------------------
INT 21 U - NewSpace - DEBUGGING DUMP
AX = 4414h
BX = FFFFh
Return: debugging dump written to X:\NEWSPACE.SMP
SeeAlso: AX=4413h/BX=FFFFh,AX=44FFh/BX=FFFFh
----------2144-------------------------------
INT 21 U - DR-DOS 5.0 - HISTORY BUFFER, SHARE, AND HILOAD CONTROL
AH = 44h
AL = 16h to 18h
Note: these subfunctions are identical to AX=4456h to 4458h
SeeAlso: AX=4456h,AX=4457h,AX=4458h
----------214451-----------------------------
INT 21 - Concurrent DOS v3.2+ - INSTALLATION CHECK
AX = 4451h
Return: CF set if not Concurrent DOS
AX = error code (see AH=59h)
CF clear if successful
AH = single-tasking/multitasking nature
10h single-tasking
AL = operating system version ID (see AX=4452h)
14h multitasking
AL = operating system version ID
32h Concurrent PC DOS 3.2
41h Concurrent DOS 4.1
50h Concurrent DOS/XM 5.0 or Concurrent DOS/386 1.1
60h Concurrent DOS/XM 6.0 or Concurrent DOS/386 2.0
62h Concurrent DOS/XM 6.2 or Concurrent DOS/386 3.0
66h DR Multiuser DOS 5.1
Notes: as of Concurrent DOS/XM 5.0 (possibly earlier), the version is stored
in the environment variable VER
use this function if you are looking for multitasking capabilities,
AX=4452h for single-tasking
this function should never return the single-tasking values
SeeAlso: AX=4452h,AX=4459h
----------214452-----------------------------
INT 21 - DR-DOS 3.41+ - DETERMINE DOS TYPE/GET DR-DOS VERSION
AX = 4452h
CF set
Return: CF set if not DR-DOS
AX = error code (see AH=59h)
CF clear if DR-DOS
DX = AX = version code
AH = single-tasking/multitasking
10h single-tasking
AL = operating system version ID
60h DOS Plus
63h DR-DOS 3.41
64h DR-DOS 3.42
65h DR-DOS 5.00
67h DR-DOS 6.00
14h multitasking
AL = operating system version ID (see AX=4451h)
Notes: the DR-DOS version is stored in the environment variable VER
use this function if looking for single-tasking capabilities, AX=4451h
if looking for multitasking; this call should never return multi-
tasking values
SeeAlso: AX=4412h,AX=4451h,AX=4459h
----------214454-----------------------------
INT 21 U - DR-DOS 3.41+ - SET GLOBAL PASSWORD
AX = 4454h
DS:DX -> password string (blank-padded to 8 characters)
Desc: Specify the master password for accessing files.
SeeAlso: AX=4303h,AX=4414h
----------214456-----------------------------
INT 21 U - DR-DOS 5.0+ - HISTORY BUFFER CONTROL
AX = 4456h
DL = flag
bit 0: 1 = command history buffers
0 = set to application
Return: AL = ??? (20h if DL bit 0 set, A0h if clear (DR-DOS 6.0))
Note: This was seen called by COMMAND.COM of DR-DOS 6.0
----------214457-----------------------------
INT 21 U - DR-DOS 5.0+ - SHARE/HILOAD CONTROL
AX = 4457h
DH = subfunction
00h enable/disable SHARE
DL = 00h disable
= 01h enable
else Return: AX = ???
01h get HILOAD status
Return: AX = status
0000h off
0001h on
02h set HILOAD status
DL = new state (00h off, 01h on)
Return: AX = ???
other
Return: AX = ???
Note: This was seen called by COMMAND.COM of DR-DOS 6.0
SeeAlso: AX=4457h/DX=FFFFh
----------214457DXFFFF-----------------------
INT 21 U - DR-DOS 6.0 - GET SHARE STATUS
AX = 4457h
DX = FFFFh
Return: AX = SHARE status
SeeAlso: INT 2F/AX=1000h
----------214458-----------------------------
INT 21 U - DR-DOS 5.0+ internal - GET POINTER TO TABLE OF ???
AX = 4458h
Return: ES:BX -> internal table (see below)
AX = ??? (0B50h for DR-DOS 5.0, 0A56h for DR-DOS 6.0)
SeeAlso: AX=4452h
Format of internal table:
Offset Size Description
00h DWORD pointer to ???
04h 7 BYTEs ???
0Bh WORD K of extended memory at startup
0Dh BYTE number of far jump entry points
0Eh WORD segment containing far jumps to DR-DOS entry points (see below)
10h WORD ???
12h WORD pointer to segment of environment variables set in CONFIG,
or 0000h if already used (DR-DOS 6.0 only)
14h ??? ???
Note: the segment used for the DR-DOS 6.0 CONFIG environment variables
(excluding COMSPEC, VER and OS) is only useful for programs/drivers
called from CONFIG.SYS. The word is set to zero later and the area
lost.
Format of jump table for DR-DOS 5.0-6.0:
Offset Size Description
00h 5 BYTEs far jump to entry point corresponding to CP/M CALL 5
05h 5 BYTEs far jump to entry point corresponding to INT 20
0Ah 5 BYTEs far jump to entry point corresponding to INT 21
0Fh 5 BYTEs far jump to entry point corresponding to ???
14h 5 BYTEs far jump to entry point corresponding to ???
19h 5 BYTEs far jump to entry point corresponding to ???
1Eh 5 BYTEs far jump to entry point corresponding to ???
23h 5 BYTEs far jump to entry point corresponding to ???
28h 5 BYTEs far jump to entry point corresponding to ???
2Dh 5 BYTEs far jump to entry point corresponding to ???
32h 5 BYTEs far jump to entry point corresponding to ??? (IRET)
37h 5 BYTEs far jump to entry point corresponding to ??? (IRET)
3Ch 5 BYTEs far jump to entry point corresponding to ??? (IRET)
41h 5 BYTEs far jump to entry point corresponding to ??? (IRET)
46h 5 BYTEs far jump to entry point corresponding to ??? (IRET)
4Bh 5 BYTEs far jump to entry point corresponding to ???
----------214459-----------------------------
INT 21 - DR MultiUser DOS 5.0 - API
AX = 4459h
CL = function (see INT E0"CP/M")
DS,DX = parameters
Notes: DR-DOS 5.0 returns CF set and AX=0001h
this API is also available on INT E0
SeeAlso: AX=4452h,INT E0"CP/M"
----------2144FFBXFFFF-----------------------
INT 21 U - NewSpace - ???
AX = 44FFh
BX = FFFFh
DX = ???
Note: NewSpace is a TSR by Isogon Corporation which automatically compresses
all files as they are written and decompresses them as they are read
SeeAlso: AX=4414h/BX=FFFFh
----------2145-------------------------------
INT 21 - DOS 2+ - "DUP" - DUPLICATE FILE HANDLE
AH = 45h
BX = file handle
Return: CF clear if successful
AX = new handle
CF set on error
AX = error code (04h,06h) (see AH=59h)
Notes: moving file pointer for either handle will also move it for the other,
because both will refer to the same system file table
for DOS versions prior to 3.3, file writes may be forced to disk by
duplicating the file handle and closing the duplicate
SeeAlso: AH=3Dh,AH=46h
----------2146-------------------------------
INT 21 - DOS 2+ - "DUP2", "FORCEDUP" - FORCE DUPLICATE FILE HANDLE
AH = 46h
BX = file handle
CX = file handle to become duplicate of first handle
Return: CF clear if successful
CF set on error
AX = error code (04h,06h) (see AH=59h)
Notes: closes file with handle CX if it is still open
DOS 3.30 hangs if BX=CX on entry
moving file pointer for either handle will also move it for the other,
because both will refer to the same system file table
SeeAlso: AH=3Dh,AH=45h
----------2147-------------------------------
INT 21 - DOS 2+ - "CWD" - GET CURRENT DIRECTORY
AH = 47h
DL = drive number (00h = default, 01h = A:, etc)
DS:SI -> 64-byte buffer for ASCIZ pathname
Return: CF clear if successful
AX = 0100h (undocumented)
CF set on error
AX = error code (0Fh) (see AH=59h)
Notes: the returned path does not include a drive or the initial backslash
many Microsoft products for Windows rely on AX being 0100h on success
under the FlashTek X-32 DOS extender, the buffer pointer is in DS:ESI
SeeAlso: AH=19h,AH=3Bh,INT 15/AX=DE25h
----------2148-------------------------------
INT 21 - DOS 2+ - ALLOCATE MEMORY
AH = 48h
BX = number of paragraphs to allocate
Return: CF clear if successful
AX = segment of allocated block
CF set on error
AX = error code (07h,08h) (see AH=59h)
BX = size of largest available block
Notes: DOS 2.1-5.0 coalesces free blocks while scanning for a block to
allocate
.COM programs are initially allocated the largest available memory
block, and should free some memory with AH=49h before attempting any
allocations
under the FlashTek X-32 DOS extender, EBX contains a protected-mode
near pointer to the allocated block on a successful return
SeeAlso: AH=49h,AH=4Ah,AH=58h,AH=83h
----------2149-------------------------------
INT 21 - DOS 2+ - FREE MEMORY
AH = 49h
ES = segment of block to free
Return: CF clear if successful
CF set on error
AX = error code (07h,09h) (see AH=59h)
Notes: apparently never returns an error 07h, despite official docs; DOS 3.30
code contains only an error 09h exit
DOS 2.1-5.0 does not coalesce adjacent free blocks when a block is
freed, only when a block is allocated or resized
SeeAlso: AH=48h,AH=4Ah
----------214A-------------------------------
INT 21 - DOS 2+ - RESIZE MEMORY BLOCK
AH = 4Ah
BX = new size in paragraphs
ES = segment of block to resize
Return: CF clear if successful
CF set on error
AX = error code (07h,08h,09h) (see AH=59h)
BX = maximum paragraphs available for specified memory block
Notes: under DOS 2.1-5.0, if there is insufficient memory to expand the block
as much as requested, the block will be made as large as possible
DOS 2.1-5.0 coalesces any free blocks immediately following the block
to be resized
SeeAlso: AH=48h,AH=49h,AH=83h
----------214B-------------------------------
INT 21 - DOS 2+ - "EXEC" - LOAD AND/OR EXECUTE PROGRAM
AH = 4Bh
AL = type of load
00h load and execute
01h load but do not execute
03h load overlay
04h load and execute in background (European MSDOS 4.0 only)
"Exec & Go" (see also AH=80h)
DS:DX -> ASCIZ program name (must include extension)
ES:BX -> parameter block (see below)
CX = mode (subfunction 04h only)
0000h child placed in zombie mode after termination
0001h child's return code discarded on termination
Return: CF clear if successful
BX,DX destroyed
if subfunction 01h, process ID set to new program's PSP; get with
INT 21/AH=62h
CF set on error
AX = error code (01h,02h,05h,08h,0Ah,0Bh) (see AH=59h)
Notes: DOS 2.x destroys all registers, including SS:SP
for functions 00h and 01h, the calling process must ensure that there
is enough unallocated memory available; if necessary, by releasing
memory with AH=49h or AH=4Ah
for function 01h, the AX value to be passed to the child program is put
on top of the child's stack
for function 03h, DOS assumes that the overlay is being loaded into
memory allocated by the caller
function 01h was undocumented prior to the release of DOS 5.0
some versions (such as DR-DOS 6.0) check the parameters and parameter
block and return an error if an invalid value (such as an offset of
FFFFh) is found
background programs under European MSDOS 4.0 must use the new
executable format
new executables begin running with the following register values
AX = environment segment
BX = offset of command tail in environment segment
CX = size of automatic data segment (0000h = 64K)
ES,BP = 0000h
DS = automatic data segment
SS:SP = initial stack
the command tail corresponds to an old executable's PSP:0081h and
following, except that the 0Dh is turned into a NUL (00h); new
format executables have no PSP
under the FlashTek X-32 DOS extender, only function 00h is supported
and the pointers are passed in DS:EDX and ES:EBX
BUGS: DOS 2.00 assumes that DS points at the current program's PSP
Load Overlay (subfunction 03h) loads up to 512 bytes too many if the
file contains additional data after the actual overlay
SeeAlso: AX=4B05h,AH=4Ch,AH=4Dh,AH=64h"OS/2",AH=8Ah,INT 2E
Format of EXEC parameter block for AL=00h,01h,04h:
Offset Size Description
00h WORD segment of environment to copy for child process (copy caller's
environment if 0000h)
02h DWORD pointer to command tail to be copied into child's PSP
06h DWORD pointer to first FCB to be copied into child's PSP
0Ah DWORD pointer to second FCB to be copied into child's PSP
0Eh DWORD (AL=01h) will hold subprogram's initial SS:SP on return
12h DWORD (AL=01h) will hold entry point (CS:IP) on return
Format of EXEC parameter block for AL=03h:
Offset Size Description
00h WORD segment at which to load overlay
02h WORD relocation factor to apply to overlay if in .EXE format
Format of EXEC parameter block for FlashTek X-32:
Offset Size Description
00h PWORD 48-bit far pointer to environment string
06h PWORD 48-bit far pointer to command tail string
Format of .EXE file header:
Offset Size Description
00h 2 BYTEs .EXE signature, either "MZ" or "ZM" (5A4Dh or 4D5Ah)
02h WORD number of bytes in last 512-byte page of executable
04h WORD total number of 512-byte pages in executable (includes any
partial last page)
06h WORD number of relocation entries
08h WORD header size in paragraphs
0Ah WORD minimum paragraphs of memory to allocation in addition to
executable's size
0Ch WORD maximum paragraphs to allocate in addition to executable's size
0Eh WORD initial SS relative to start of executable
10h WORD initial SP
12h WORD checksum (one's complement of sum of all words in executable)
14h DWORD initial CS:IP relative to start of executable
18h WORD offset within header of relocation table (40h for New EXE)
1Ah WORD overlay number (normally 0000h = main program)
---new executable---
1Ch 4 BYTEs ???
20h WORD behavior bits
22h 26 BYTEs reserved for additional behavior info
3Ch DWORD offset of new executable header within disk file
---Borland TLINK---
1Ch 2 BYTEs ??? (apparently always 01h 00h)
1Eh BYTE signature FBh
1Fh BYTE TLINK version (major in high nybble, minor in low nybble)
20h 2 BYTEs ??? (v2.0 apparently always 72h 6Ah, v3.0+ seems always 6Ah 72h)
---ARJ self-extracting archive---
1Ch 4 BYTEs signature "RJSX"
---LZEXE 0.91 compressed executable---
1Ch 4 BYTEs signature "LZ91"
---PKLITE compressed executable---
1Ch 2 BYTEs ???
1Eh 6 BYTEs signature "PKLITE" (followed by copyright message)
---LHarc 1.x self-extracting archive---
1Ch 4 BYTEs unused???
20h 3 BYTEs jump to start of extraction code
23h 2 BYTEs ???
25h 12 BYTEs signature "LHarc's SFX "
---LHA 2.x self-extracting archive---
1Ch 8 BYTEs ???
24h 10 BYTEs signature "LHA's SFX "
---other linkers---
1Ch var optional information
---
N N DWORDs relocation items
Notes: if word at offset 02h is 4, it should be treated as 00h, since pre-1.10
versions of the MS linker set it that way
if both minimum and maximum allocation (offset 0Ah/0Ch) are zero, the
program is loaded as high in memory as possible
the maximum allocation is set to FFFFh by default
Format of new executable header:
Offset Size Description
00h 2 BYTEs "NE" (4Eh 45h) signature
02h 2 BYTEs linker version (major, then minor)
04h WORD offset from start of this header to entry table (see below)
06h WORD length of entry table in bytes
08h DWORD file load CRC (0 in Borland's TPW)
0Ch BYTE program flags
bits 0-1 DGROUP type
0 = none
1 = single shared
2 = multiple (unshared)
3 = (null)
bit 2: global initialization
bit 3: protected mode only
bit 4: 8086 instructions
bit 5: 80286 instructions
bit 6: 80386 instructions
bit 7: 80x87 instructions
0Dh BYTE application flags
bits 0-2: application type
001 full screen (not aware of Windows/P.M. API)
010 compatible with Windows/P.M. API
011 uses Windows/P.M. API
bit 3: is a Family Application (OS/2)
bit 5: 0=executable, 1=errors in image
bit 6: non-conforming program (valid stack is not maintained)
bit 7: DLL or driver rather than application
(SS:SP info invalid, CS:IP points at FAR init routine
called with AX=module handle which returns AX=0000h
on failure, AX nonzero on successful initialization)
0Eh WORD auto data segment index
10h WORD initial local heap size
12h WORD initial stack size (added to data seg, 0000h if SS != DS)
14h DWORD program entry point (CS:IP), "CS" is index into segment table
18h DWORD initial stack pointer (SS:SP), "SS" is segment index
if SS=automatic data segment and SP=0000h, the stack pointer is
set to the top of the automatic data segment, just below the
local heap
1Ch WORD segment count
1Eh WORD module reference count
20h WORD length of nonresident names table in bytes
22h WORD offset from start of this header to segment table (see below)
24h WORD offset from start of this header to resource table
26h WORD offset from start of this header to resident names table
28h WORD offset from start of this header to module reference table
2Ah WORD offset from start of this header to imported names table
(array of counted strings, terminated with a string of length
00h)
2Ch DWORD offset from start of file to nonresident names table
30h WORD count of moveable entry point listed in entry table
32h WORD file alignment size shift count
0 is equivalent to 9 (default 512-byte pages)
34h WORD number of resource table entries
36h BYTE target operating system
00h unknown
01h OS/2
02h Windows
03h European MSDOS 4.x
04h Windows 386
05h BOSS (Borland Operating System Services)
37h BYTE other EXE flags
bit 0: supports long filenames
bit 1: 2.X protected mode
bit 2: 2.X proportional font
bit 3: gangload area
38h WORD offset to return thunks or start of gangload area
3Ah WORD offset to segment reference thunks or length of gangload area
3Ch WORD minimum code swap area size
3Eh 2 BYTEs expected Windows version (minor version first)
Format of Codeview trailer (at end of executable):
Offset Size Description
00h WORD signature 4E42h ('NB')
02h WORD Microsoft debug info version number
04h DWORD Codeview header offset
Format of new executable segment table record:
00h WORD offset in file (shift left by alignment shift to get byte offs)
02h WORD length of image in file (0000h = 64K)
04h WORD attributes
bit 0: data segment rather than code segment
bit 1: unused???
bit 2: real mode
bit 3: iterated
bit 4: movable
bit 5: sharable
bit 6: preloaded rather than demand-loaded
bit 7: execute-only (code) or read-only (data)
bit 8: relocations (directly following code for this segment)
bit 9: debug info present
bits 10,11: 80286 DPL bits
bit 12: discardable
bits 13-15: discard priority
06h WORD number of bytes to allocate for segment (0000h = 64K)
Note: the first segment table entry is entry number 1
Format of new executable entry table item (list):
Offset Size Description
00h BYTE number of entry points (00h if end of entry table list)
01h BYTE segment number (00h if end of entry table list)
02h 3N BYTEs entry records
Offset Size Description
00h BYTE flags
bit 0: exported
bit 1: single data
bits 2-7: unused???
01h WORD offset within segment
Format of new executable relocation data (immediately follows segment image):
Offset Size Description
00h WORD number of relocation items
02h 8N BYTEs relocation items
Offset Size Description
00h BYTE relocation type
00h LOBYTE
02h BASE
03h PTR
05h OFFS
0Bh PTR48
0Dh OFFS32
01h BYTE flags
bit 2: additive
02h WORD offset within segment
04h WORD target address segment
06h WORD target address offset
Format of new executable resource data:
Offset Size Description
00h WORD alignment shift count for resource data
02h N RECORDs resources
Format of resource record:
Offset Size Description
00h WORD type ID
0000h if end of resource records
>= 8000h if integer type
else offset from start of resource table to type string
02h WORD number of resources of this type
04h DWORD reserved for runtime use
08h N Resources (see below)
Note: resource type and name strings are stored immediately following the
resource table, and are not null-terminated
Format of new executable resource entry:
Offset Size Description
00h WORD offset in alignment units from start of file to contents of
the resource data
02h WORD length of resource image in bytes
04h WORD flags
bit 4: moveable
bit 5: shareable
bit 6: preloaded
06h WORD resource ID
>= 8000h if integer resource
else offset from start of resource table to resource string
08h DWORD reserved for runtime use
Notes: resource type and name strings are stored immediately following the
resource table, and are not null-terminated
strings are counted strings, with a string of length 0 indicating the
end of the resource table
Format of new executable module reference table [one bundle of entries]:
Offset Size Description
00h BYTE number of records in this bundle (00h if end of table)
01h BYTE segment indicator
00h unused
FFh movable segment, segment number is in entry
else segment number of fixed segment
02h N RECORDs
Format of segment record
Offset Size Description
00h BYTE flags
bit 0: entry is exported
bit 1: entry uses global (shared) data
bits 7-3: number of parameter words
---fixed segment---
01h WORD offset
---moveable segment---
01h 2 BYTEs INT 3F instruction (CDh 3Fh)
03h BYTE segment number
05h WORD offset
Note: table entries are numbered starting from 1
Format of new executable resident/nonresident name table entry:
Offset Size Description
00h BYTE length of string (00h if end of table)
01h N BYTEs ASCII text of string
N+1 WORD ordinal number (index into entry table)
Notes: the first string in the resident name table is the module name; the
first entry in the nonresident name table is the module description
the strings are case-sensitive; if the executable was linked with
/IGNORECASE, all strings are in uppercase
Format of Linear Executable (enhanced mode executable) header:
Offset Size Description
00h 2 BYTEs "LE" (4Ch 45h) signature
02h BYTE byte order (00h = little-endian, nonzero = big-endian)
03h BYTE word order (00h = little-endian, nonzero = big-endian)
04h DWORD executable format level
08h WORD CPU type (see also INT 15/AH=C9h)
01h Intel 80286 or upwardly compatible
02h Intel 80386 or upwardly compatible
03h Intel 80486 or upwardly compatible
04h Intel 80586 or upwardly compatible
20h Intel i860 (N10) or compatible
21h Intel "N11" or compatible
40h MIPS Mark I (R2000, R3000) or compatible
41h MIPS Mark II (R6000) or compatible
42h MIPS Mark III (R4000) or compatible
0Ah WORD target operating system
01h OS/2
02h Windows
03h DOS4.x
04h Windows 386
0Ch DWORD module version
10h DWORD module type
bit 2: initialization (only for DLLs)
0 = global
1 = per-process
bit 4: no internal fixups in executable image
bit 5: no external fixups in executable image
bits 8,9,10:
0 = unknown
1 = incompatible with PM windowing \
2 = compatible with PM windowing > (only for
3 = uses PM windowing API / programs)
bit 13: module not loadable (only for programs)
bit 15: module is DLL rather than program
14h DWORD number of memory pages
18h Initial CS:EIP
DWORD object number
DWORD offset
20h Initial SS:ESP
DWORD object number
DWORD offset
28h DWORD memory page size
2Ch DWORD bytes on last page
30h DWORD fixup section size
34h DWORD fixup section checksum
38h DWORD loader section size
3Ch DWORD loader section checksum
40h DWORD offset of object table (see below)
44h DWORD object table entries
48h DWORD object page map table offset
4CH DWORD object iterate data map offset
50h DWORD resource table offset
54h DWORD resource table entries
58h DWORD resident names table offset
5Ch DWORD entry table offset
60h DWORD module directives table offset
64h DWORD Module Directives entries
68h DWORD Fixup page table offset
6Ch DWORD Fixup record table offset
70h DWORD imported modules name table offset
74h DWORD imported modules count
78h DWORD imported procedures name table offset
7Ch DWORD per-page checksum table offset
80h DWORD data pages offset
84h DWORD preload page count
88h DWORD non-resident names table offset
8Ch DWORD non-resident names table length
90h DWORD non-resident names checksum
94h DWORD automatic data object
98h DWORD debug information offset
9Ch DWORD debug information length
A0h DWORD preload instance pages number
A4h DWORD demand instance pages number
A8h DWORD extra heap allocation
ACh ??? (at most 24 additional bytes here)
Note: used by EMM386.EXE, QEMM, and Windows 3.0 Enhanced Mode drivers
Format of object table entry:
Offset Size Description
00h DWORD virtual size in bytes
04h DWORD relocation base address
08h DWORD object flags
bit 0: readable
bit 1: writable
bit 2: executable
bit 3: resource
bit 4: discardable
bit 5: shared
bit 6: preloaded
bit 7: invalid
bit 8-9: type
00 normal
01 zero-filled
10 resident
11 resident/contiguous
bit 10: "RESIDENT/LONG_LOCKABLE"
bit 11: reserved???
bit 12: "16:16_ALIAS"
bit 13: "BIG" (32-bit???)
bit 14: conforming
bit 15: "OBJECT_I/O_PRIVILEGE_LEVEL"
bits 16-31: reserved
0Ch DWORD page map index
10h DWORD page map entries
10h 4 BYTEs ??? (apparently always zeros)
Format of object page map table entry:
Offset Size Description
00h 4 BYTEs ???
Format of resident names table entry:
Offset Size Description
00h BYTE length of name
01h N BYTEs name
N+1 3 BYTEs ???
Format of linear executable entry table:
Offset Size Description
00h BYTE number of entries in table
01h 10 BYTEs per entry
Offset Size Description
00h BYTE bit flags
bit 1: 32-bit entry
01h WORD object number
03h BYTE bit flags
bit 0: exported
bit 1: ???
04h DWORD offset of entry point
08h 2 BYTEs ???
Format of Borland debugging information header (following load image):
Offset Size Description
00h WORD signature 52FBh
02h WORD version ID
04h DWORD size of name pool in bytes
08h WORD number of names in namem pool
0Ah WORD number of type entries
0Ch WORD number of structure members
0Eh WORD number of symbols
10h WORD number of global symbols
12h WORD number of modules
14h WORD number of locals (optional)
16h WORD number of scopes in table
18h WORD number of line-number entries
1Ah WORD number of include files
1Ch WORD number of segment records
1Eh WORD number of segment/file correlations
20h DWORD size of load image after removing uninitialized data and debug
info
24h DWORD debugger hook; pointer into debugged program whose meaning
depends on program flags
28h BYTE program flags
bit 0: case-sensitive link
bit 1: pascal overlay program
29h WORD no longer used
2Bh WORD size of data pool in bytes
2Dh BYTE padding
2Eh WORD size of following header extension (currently 00h, 10h, or 20h)
30h WORD number of classes
32h WORD number of parents
34h WORD number of global classes (currently unused)
36h WORD number of overloads (currently unused)
38h WORD number of scope classes
3Ah WORD number of module classes
3Ch WORD number of coverage offsets
3Eh DWORD offset relative to symbol base of name pool
42h WORD number of browser information records
44h WORD number of optimized symbol records
46h WORD debugging flags
48h 8 BYTEs padding
Note: additional information on the Borland debugging info may be found in
Borland's Open Architecture Handbook
----------214B-------------------------------
INT 21 - ELRES v1.0 only - INSTALLATION CHECK
AH = 4Bh
DS:DX = 0000h:0000h
Return: ES:BX -> ELRES history structure (see AH=2Bh/CX=454Ch)
DX = DABEh (signature, DAve BEnnett)
Note: ELRES is an MSDOS return code (errorlevel) recorder by David H. Bennett
SeeAlso: AH=2Bh/CX=454Ch
----------214B04-----------------------------
INT 21 - VIRUS - "MG", "699"/"Thirteen Minutes" - INSTALLATION CHECK
AX = 4B04h
Return: CF clear if "MG" resident
AX = 044Bh if "699"/"Thirteen Minutes" resident
SeeAlso: AX=4243h,AX=4B25h
----------214B05-----------------------------
INT 21 - DOS 5.0 - SET EXECUTION STATE
AX = 4B05h
DS:DX -> execution state structure (see below)
Return: CF clear if successful
AX = 0000h
CF set on error
AX = error code (see AH=59h)
Note: used by programs which intercept AX=4B00h to prepare new programs for
execution (including setting the DOS version number). No DOS, BIOS
or other software interrupt may be called after return from this call
before commencement of the child process. If DOS is running in the
HMA, A20 is turned off on return from this call.
SeeAlso: AH=4Bh
Format of execution state structure:
Offset Size Description
00h WORD reserved (00h)
02h WORD type flags
bit 0: program is an .EXE
1: program is an overlay
04h DWORD pointer to ASCIZ name of program file
08h WORD PSP segment of new program
0Ah DWORD starting CS:IP of new program
0Eh DWORD program size including PSP
----------214B25-----------------------------
INT 21 - VIRUS - "1063"/"Mono" - INSTALLATION CHECK
AX = 4B25h
Return: DI = 1234h if resident
SeeAlso: AX=4B04h,AX=4B40h
----------214B40-----------------------------
INT 21 - VIRUS - "Plastique"/"AntiCad" - INSTALLATION CHECK
AX = 4B40h
Return: AX = 5678h if resident
SeeAlso: AX=4B25h,AX=4B41h,AX=4B4Ah
----------214B41-----------------------------
INT 21 - VIRUS - "Plastique"/"AntiCad" - ???
AX = 4B41h
???
Return: ???
SeeAlso: AX=4B40h
----------214B4A-----------------------------
INT 21 - VIRUS - "Jabberwocky" - INSTALLATION CHECK
AX = 4B4Ah
Return: AL = 57h if resident
SeeAlso: AX=4B40h,AX=4B4Bh
----------214B4B-----------------------------
INT 21 - VIRUS - "Horse-2" - INSTALLATION CHECK
AX = 4B4Bh
Return: CF clear if resident
SeeAlso: AX=4B4Ah,AX=4B4Dh
----------214B4D-----------------------------
INT 21 - VIRUS - "Murphy-2", "Patricia"/"Smack" - INSTALLATION CHECK
AX = 4B4Dh
Return: CF clear if resident
SeeAlso: AX=4B4Ah,AX=4B50h
----------214B50-----------------------------
INT 21 - VIRUS - "Plastique-2576"/"AntiCad-2576" - INSTALLATION CHECK
AX = 4B50h
Return: AX = 1234h if resident
SeeAlso: AX=4B4Dh,AX=4B53h,AX=4B60h
----------214B53-----------------------------
INT 21 - VIRUS - "Horse" - INSTALLATION CHECK
AX = 4B53h
Return: CF clear if resident
SeeAlso: AX=4B50h,AX=4B55h
----------214B55-----------------------------
INT 21 - VIRUS - "Sparse" - INSTALLATION CHECK
AX = 4B55h
Return: AX = 1231h if resident
SeeAlso: AX=4B53h,AX=4B59h
----------214B59-----------------------------
INT 21 - VIRUS - "Murphy-1", "Murphy-4" - INSTALLATION CHECK
AX = 4B59h
Return: CF clear if resident
SeeAlso: AX=4B50h,AX=4B5Eh
----------214B5E-----------------------------
INT 21 - VIRUS - "Brothers" - INSTALLATION CHECK
AX = 4B5Eh
Return: CF clear if resident
SeeAlso: AX=4B59h,AX=4B87h
----------214B60-----------------------------
INT 21 - VIRUS - "Plastique-2576"/"AntiCad-2576" - ???
AX = 4B60h
???
Return: ???
SeeAlso: AX=4B50h
----------214B87-----------------------------
INT 21 - VIRUS - "Shirley" - INSTALLATION CHECK
AX = 4B87h
Return: AX = 6663h if resident
SeeAlso: AX=4B5Eh,AX=4B95h
----------214B95-----------------------------
INT 21 - VIRUS - "Zherkov-1882" - INSTALLATION CHECK
AX = 4B95h
Return: AX = 1973h if resident
SeeAlso: AX=4B87h,AX=4BA7h
----------214BA7-----------------------------
INT 21 - VIRUS - "1876"/"Dash-em" - INSTALLATION CHECK
AX = 4BA7h
Return: AX = B459h if resident
SeeAlso: AX=4B95h,AX=4BAAh
----------214BAA-----------------------------
INT 21 - VIRUS - "Nomenklatura" - INSTALLATION CHECK
AX = 4BAAh
Return: CF clear if resident
SeeAlso: AX=4BA7h,AX=4BAFh
----------214BAF-----------------------------
INT 21 - VIRUS - "948"/"Screenplus1", "Magnitogorsk" - INSTALLATION CHECK
AX = 4BAFh
Return: AL = AFh if "Magnitogorsk" resident
AL = FAh if "948"/"Screenplus1" resident
SeeAlso: AX=4BAAh,AX=4BDDh
----------214BDD-----------------------------
INT 21 - VIRUS - "Lozinsky"/"Zherkov" - INSTALLATION CHECK
AX = 4BDDh
Return: AX = 1234h
SeeAlso: AX=4BAFh,AX=4BFEh
----------214BEE-----------------------------
INT 21 - F-DRIVER.SYS v1.14+ - GRAB INT 21
AX = 4BEEh
Return: AX = 1234h if grab successful
= 2345h if failed (INT 21 grabbed previously)
Notes: F-DRIVER.SYS is part of the F-PROT virus/trojan protection package by
Fridrik Skulason
when called the first time, this function moves the INT 21 monitoring
code from its original location in the INT 21 chain to be the first
thing called by INT 21. This is the mechanism used by F-NET.
SeeAlso: INT 2F/AX=4653h
----------214BF0-----------------------------
INT 21 - DIET v1.10+ (Overlay Mode) - INSTALLATION CHECK
AX = 4BF0h
Return: CF clear if installed
AX = 899Dh
Note: DIET is an executable-compression program
SeeAlso: AX=4BF1h
----------214BF1-----------------------------
INT 21 - DIET v1.10+ (Overlay Mode) - EXPAND PROGRAM???
AX = 4BF1h
Return: ???
SeeAlso: AX=4BF0h
----------214BFE-----------------------------
INT 21 - VIRUS - "Hitchcock", "Dark Avenger-1028", "1193" - INSTALLATION CHECK
AX = 4BFEh
Return: AX = 1234h if "Hitchcock" resident
AX = ABCDh if "1193"/"Copyright" resident
DI = 55BBh if "Dark Avenger-1028" resident
SeeAlso: AX=4BDDh,AX=4BFFh"Justice"
----------214BFF-----------------------------
INT 21 - VIRUS - "USSR-707", "Justice", "Europe 92" - INSTALLATION CHECK
AX = 4BFFh
Return: BL = FFh if "USSR-707" resident
DI = 55AAh if "Justice" resident
CF clear if "Europe 92" resident
SeeAlso: AX=4BFEh,AX=4BFFh"Cascade",AX=5252h
----------214BFFSI0000-----------------------
INT 21 - VIRUS - "Cascade" - INSTALLATION CHECK
AX = 4BFFh
SI = 0000h
DI = 0000h
Return: DI = 55AAh if installed
SeeAlso: AX=4BFFh"Justice",AX=5252h
----------214C-------------------------------
INT 21 - DOS 2+ - "EXIT" - TERMINATE WITH RETURN CODE
AH = 4Ch
AL = return code
Return: never returns
Notes: unless the process is its own parent (see AH=26h, offset 16h in PSP),
all open files are closed and all memory belonging to the process
is freed
all network file locks should be removed before calling this function
SeeAlso: AH=00h,AH=26h,AH=4Bh,AH=4Dh,INT 15/AH=12h/BH=02h,INT 20,INT 22
SeeAlso: INT 60/DI=0601h
----------214D-------------------------------
INT 21 - DOS 2+ - GET RETURN CODE
AH = 4Dh
Return: AH = termination type
00h normal (INT 20,INT 21/AH=00h, or INT 21/AH=4Ch)
01h control-C abort
02h critical error abort
03h terminate and stay resident (INT 21/AH=31h or INT 27)
AL = return code
Notes: the word in which DOS stores the return code is cleared after being
read by this function, so the return code can only be retrieved once
this call should not be used if the child was started with AX=4B04h;
use AH=8Ah instead
SeeAlso: AH=4Bh,AH=4Ch,AH=8Ah
----------214E-------------------------------
INT 21 - DOS 2+ - "FINDFIRST" - FIND FIRST MATCHING FILE
AH = 4Eh
AL = special flag for use by APPEND (see note below)
CX = file attribute mask (see AX=4301h) (bits 0 and 5 ignored)
DS:DX -> ASCIZ file specification (may include path and wildcards)
Return: CF clear if successful
[DTA] = FindFirst data block (see below)
CF set on error
AX = error code (02h,03h,12h) (see AH=59h)
Notes: for search attributes other than 08h, all files with at MOST the
specified combination of hidden, system, and directory attributes
will be returned. Under DOS 2.x, searching for attribute 08h
(volume label) will also return normal files, while under DOS 3+
only the volume label (if any) will be returned.
this call also returns successfully if given the name of a character
device without wildcards. DOS 2.x returns attribute 00h, size 0,
and the current date and time. DOS 3+ returns attribute 40h and the
current date and time.
immediately after an INT 2F/AX=B711h (APPEND return found name), the
name at DS:DX will be overwritten; if AL=00h on entry, the actual
found pathname will be stored, otherwise, the actual found path
will be prepended to the original filespec without a path.
under LANtastic, this call may be used to obtain a list of a server's
shared resources by searching for "\\SERVER\*.*"; a list of printer
resources may be obtained by searching for "\\SERVER\@*.*"
under the FlashTek X-32 DOS extender, the filespec pointer is in DS:EDX
BUG: under DOS 3.x and 4.x, the second and subsequent calls to this function
with a character device name (no wildcards) and search attributes
which include the volume-label bit (08h) will fail unless there is
an intervening DOS call which implicitly or explicity performs a
directory search without the volume-label bit. Such implicit
searches are performed by CREATE (AH=3Ch), OPEN (AH=3Dh), UNLINK
(AH=41h), and RENAME (AH=56h)
SeeAlso: AH=11h,AH=4Fh,AX=4301h,INT 2F/AX=111Bh,INT 2F/AX=B711h
Format of FindFirst data block:
Offset Size Description
---PCDOS 3.10, PCDOS 4.01, MSDOS 3.2/3.3/5.0---
00h BYTE drive letter (bits 0-6), remote if bit 7 set
01h 11 BYTEs search template
0Ch BYTE search attributes
---DOS 2.x (and some DOS 3.x???)---
00h BYTE search attributes
01h BYTE drive letter
02h 11 BYTEs search template
---WILDUNIX.COM---
00h 12 BYTEs 15-character wildcard search pattern and drive letter (packed)
0Ch BYTE search attributes
---DOS 2.x and most 3.x---
0Dh WORD entry count within directory
0Fh DWORD pointer to DTA???
13h WORD cluster number of start of parent directory
---PCDOS 4.01, MSDOS 3.2/3.3/5.0---
0Dh WORD entry count within directory
0Fh WORD cluster number of start of parent directory
11h 4 BYTEs reserved
---all versions, documented fields---
15h BYTE attribute of file found
16h WORD file time
bits 11-15: hour
bits 5-10: minute
bits 0-4: seconds/2
18h WORD file date
bits 9-15: year-1980
bits 5-8: month
bits 0-4: day
1Ah DWORD file size
1Eh 13 BYTEs ASCIZ filename+extension
----------214E-------------------------------
INT 21 - WILDUNIX.COM internal - INSTALLATION CHECK
AH = 4Eh
DS:DX = 0000h:0000h
Return: AH = 99h if installed
Note: WILDUNIX.COM is a resident Unix-style wildcard expander by Steve
Hosgood and Terry Barnaby
----------214F-------------------------------
INT 21 - DOS 2+ - "FINDNEXT" - FIND NEXT MATCHING FILE
AH = 4Fh
[DTA] = data block from previous FindFirst or FindNext call
Return: CF clear if successful
CF set on error
AX = error code (12h) (see AH=59h)
SeeAlso: AH=12h,AH=4Eh
----------2150-------------------------------
INT 21 - DOS 2+ internal - SET CURRENT PROCESS ID (SET PSP ADDRESS)
AH = 50h
BX = segment of PSP for new process
Notes: DOS uses the current PSP address to determine which processes own files
and memory; it corresponds to process identifiers used by other OSs
under DOS 2.x, this function cannot be invoked inside an INT 28h
handler without setting the Critical Error flag
under DOS 3+, this function does not use any of the DOS-internal stacks
and may thus be called at any time, even during another INT 21h call
some Microsoft applications use segments of 0000h and FFFFh; although
one should only call this function with valid PSP addresses, any
program hooking it should be prepared to handle invalid addresses
supported by OS/2 compatibility box
this call was undocumented prior to the release of DOS 5.0
SeeAlso: AH=26h,AH=51h,AH=62h
----------2151-------------------------------
INT 21 - DOS 2+ internal - GET CURRENT PROCESS ID (GET PSP ADDRESS)
AH = 51h
Return: BX = segment of PSP for current process
Notes: DOS uses the current PSP address to determine which processes own files
and memory; it corresponds to process identifiers used by other OSs
under DOS 2.x, this function cannot be invoked inside an INT 28h
handler without setting the Critical Error flag
under DOS 3+, this function does not use any of the DOS-internal stacks
and may thus be called at any time, even during another INT 21h call
supported by OS/2 compatibility box
identical to the documented AH=62h
undocumented for DOS 2.x-4.x, but newly documented for 5.0.
SeeAlso: AH=26h,AH=50h,AH=62h
----------2152-------------------------------
INT 21 U - DOS 2+ internal - "SYSVARS" - GET LIST OF LISTS
AH = 52h
Return: ES:BX -> DOS list of lists
Note: partially supported by OS/2 v1.1 compatibility box (however, most
pointers are FFFFh:FFFFh, LASTDRIVE is FFh, and the NUL header "next"
pointer is FFFFh:FFFFh).
Format of List of Lists:
Offset Size Description
-12 WORD (DOS 3.1+) sharing retry count (see AX=440Bh)
-10 WORD (DOS 3.1+) sharing retry delay (see AX=440Bh)
-8 DWORD (DOS 3+) pointer to current disk buffer
-4 WORD (DOS 3+) pointer in DOS code segment of unread CON input
when CON is read via a handle, DOS reads an entire line,
and returns the requested portion, buffering the rest
for the next read. 0000h indicates no unread input
-2 WORD segment of first memory control block
00h DWORD pointer to first Drive Parameter Block (see AH=32h)
04h DWORD pointer to first System File Table (see below)
08h DWORD pointer to active CLOCK$ device's header
0Ch DWORD pointer to active CON device's header
---DOS 2.x---
10h BYTE number of logical drives in system
11h WORD maximum bytes/block of any block device
13h DWORD pointer to first disk buffer (see below)
17h 18 BYTEs actual NUL device driver header (not a pointer!)
NUL is always the first device on DOS's linked list of device
drivers. (see below)
---DOS 3.0---
10h BYTE number of block devices
11h WORD maximum bytes/block of any block device
13h DWORD pointer to first disk buffer (see below)
17h DWORD pointer to array of current directory structures (see below)
1Bh BYTE value of LASTDRIVE command in CONFIG.SYS (default 5)
1Ch DWORD pointer to STRING= workspace area
20h WORD size of STRING area (the x in STRING=x from CONFIG.SYS)
22h DWORD pointer to FCB table
26h WORD the y in FCBS=x,y from CONFIG.SYS
28h 18 BYTEs actual NUL device driver header (not a pointer!)
NUL is always the first device on DOS's linked list of device
drivers. (see below)
---DOS 3.1-3.3---
10h WORD maximum bytes per sector of any block device
12h DWORD pointer to first disk buffer in buffer chain (see below)
16h DWORD pointer to array of current directory structures (see below)
1Ah DWORD pointer to system FCB tables (see below)
1Eh WORD number of protected FCBs (the y in the CONFIG.SYS FCBS=x,y)
20h BYTE number of block devices installed
21h BYTE number of available drive letters (largest of 5, installed
block devices, and CONFIG.SYS LASTDRIVE=). Also size of
current directory structure array.
22h 18 BYTEs actual NUL device driver header (not a pointer!)
NUL is always the first device on DOS's linked list of device
drivers. (see below)
34h BYTE number of JOIN'ed drives
---DOS 4.x---
10h WORD maximum bytes per sector of any block device
12h DWORD pointer to disk buffer info record (see below)
16h DWORD pointer to array of current directory structures (see below)
1Ah DWORD pointer to system FCB tables (see below)
1Eh WORD number of protected FCBs (the y in the CONFIG.SYS FCBS=x,y)
(always 00h for DOS 5.0)
20h BYTE number of block devices installed
21h BYTE number of available drive letters (largest of 5, installed
block devices, and CONFIG.SYS LASTDRIVE=). Also size of
current directory structure array.
22h 18 BYTEs actual NUL device driver header (not a pointer!)
NUL is always the first device on DOS's linked list of device
drivers. (see below)
34h BYTE number of JOIN'ed drives???
35h WORD pointer within IBMDOS code segment to list of special program
names (see below)
(always 0000h for DOS 5.0)
37h DWORD pointer to FAR routine for resident IFS utility functions
(see below)
may be called by any IFS driver which does not wish to
service functions 20h or 24h-28h itself
3Bh DWORD pointer to chain of IFS (installable file system) drivers
3Fh WORD the x in BUFFERS x,y (rounded up to multiple of 30 if in EMS)
41h WORD the y in BUFFERS x,y
43h BYTE boot drive (1=A:)
44h BYTE 01h if 80386+, 00h otherwise???
45h WORD extended memory size in K
---DOS 5.0---
10h 39 BYTEs as for DOS 4.x (see above)
37h DWORD pointer to SETVER program list or 0000h:0000h
3Bh WORD ??? pointer to function in DOS CS
3Dh WORD ??? apparently 0000h if DOS loaded low, PSP of most-recently
EXECed program if DOS in HMA
3Fh 8 BYTEs as for DOS 4.x (see above)
Format of memory control block (see also below):
Offset Size Description
00h BYTE block type: 5Ah if last block in chain, otherwise 4Dh
01h WORD PSP segment of owner or
0000h if free
0006h if DR-DOS XMS UMB
0007h if DR-DOS excluded upper memory ("hole")
0008h if belongs to DOS
FFFAh if 386MAX UMB control block
FFFDh if 386MAX locked-out memory
FFFEh if 386MAX UMB (immediately follows its control block)
03h WORD size of memory block in paragraphs
05h 3 BYTEs unused
---DOS 2.x,3.x---
08h 8 BYTEs unused
---DOS 4+ ---
08h 8 BYTEs ASCII program name if PSP memory block or DR-DOS UMB,
else garbage
null-terminated if less than 8 characters
Notes: the next MCB is at segment (current + size + 1)
under DOS 3.1+, the first memory block is the DOS data segment,
containing installable drivers, buffers, etc. Under DOS 4+ it is
divided into subsegments, each with its own memory control block
(see below), the first of which is at offset 0000h.
for DOS 5.0, blocks owned by DOS may have either "SC" or "SD" in bytes
08h and 09h. "SC" is system code or locked-out inter-UMB memory,
"SD" is system data, device drivers, etc.
Some versions of DR-DOS use only seven characters of the program name,
placing a NUL in the eighth byte.
Format of MSDOS 5.0 UMB control block:
Offset Size Description
00h BYTE type: 5Ah if last block in chain, 4Dh otherwise
01h WORD first available paragraph in UMB if control block at start
of UMB, 000Ah if control block at end of UMB
03h WORD length in paragraphs of following UMB or locked-out region
05h 3 BYTEs unused
08h 8 BYTEs block type name: "UMB" if start block, "SM" if end block in UMB
Format of STARLITE (General Software's Embedded DOS) memory control block:
Offset Size Description
00h BYTE block type: 5Ah if last block in chain, otherwise 4Dh
01h WORD PSP segment of owner, 0000h if free, 0008h if belongs to DOS
03h WORD size of memory block in paragraphs
05h BYTE unused
06h WORD segment address of next memory control block (0000h if last)
08h WORD segment address of previous memory control block or 0000h
0Ah 6 BYTEs reserved
Format of DOS 4.x data segment subsegment control blocks:
Offset Size Description
00h BYTE subsegment type (blocks typically appear in this order)
"D" device driver
"E" device driver appendage
"I" IFS (Installable File System) driver
"F" FILES= control block storage area (for FILES>5)
"X" FCBS= control block storage area, if present
"C" BUFFERS EMS workspace area (if BUFFERS /X option used)
"B" BUFFERS= storage area
"L" LASTDRIVE= current directory structure array storage area
"S" STACKS= code and data area, if present (see below)
"T" INSTALL= transient code
01h WORD paragraph of subsegment start (usually the next paragraph)
03h WORD size of subsegment in paragraphs
05h 3 BYTEs unused
08h 8 BYTEs for types "D" and "I", base name of file from which the driver
was loaded (unused for other types)
Format of data at start of STACKS code segment (if present):
Offset Size Description
00h WORD ???
02h WORD number of stacks (the x in STACKS=x,y)
04h WORD size of stack control block array (should be 8*x)
06h WORD size of each stack (the y in STACKS=x,y)
08h DWORD pointer to STACKS data segment
0Ch WORD offset in STACKS data segment of stack control block array
0Eh WORD offset in STACKS data segment of last element of that array
10h WORD offset in STACKS data segment of the entry in that array for
the next stack to be allocated (initially same as value in 0Eh
and works its way down in steps of 8 to the value in 0Ch as
hardware interrupts pre-empt each other)
Note: the STACKS code segment data may, if present, be located as follows:
DOS 3.2: The code segment data is at a paragraph boundary fairly early
in the IBMBIO segment (seen at 0070:0190h)
DOS 3.3: The code segment is at a paragraph boundary in the DOS data
segment, which may be determined by inspecting the segment
pointers of the vectors for those of interrupts 02h, 08h-0Eh,
70h, 72-77h which have not been redirected by device drivers or
TSRs.
DOS 4.x: Identified by sub-segment control block type "S" within the DOS
data segment.
Format of array elements in STACKS data segment:
Offset Size Description
00h BYTE status: 00h=free, 01h=in use, 03h=corrupted by overflow of
higher stack.
01h BYTE not used
02h WORD previous SP
04h WORD previous SS
06h WORD ptr to word at top of stack (new value for SP). The word at the
top of the stack is preset to point back to this control block.
SHARE.EXE hooks (DOS 3.1-5.00):
(offsets from first system file table--pointed at by ListOfLists+04h)
Offset Size Description
-3Ch DWORD pointer to FAR routine for ???
Note: not called by MSDOS 3.3, set to 0000h:0000h by SHARE 3.3
-38h DWORD pointer to FAR routine called on opening file
on call, internal DOS location points at filename(see AX=5D06h)
Return: CF clear if successful
CF set on error
AX = DOS error code (24h) (see AH=59h)
Note: SHARE assumes DS=SS=DOS DS, direct-accesses DOS internals
to get name of file just opened
-34h DWORD pointer to FAR routine called on closing file
ES:DI -> system file table
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
does something to every lock record for file
-30h DWORD pointer to FAR routine to close all files for given computer
(called by AX=5D03h)
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
-2Ch DWORD pointer to FAR routine to close all files for given process
(called by AX=5D04h)
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
-28h DWORD pointer to FAR routine to close file by name
(called by AX=5D02h)
DS:SI -> DOS parameter list (see AX=5D00h)
DPL's DS:DX -> name of file to close
Return: CF clear if successful
CF set on error
AX = DOS error code (03h) (see AH=59h)
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
-24h DWORD pointer to FAR routine to lock region of file
call with BX = file handle
CX:DX = starting offset
SI:AX = size
Return: CF set on error
AL = DOS error code (21h) (see AH=59h)
Note: not called if file is marked as remote
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
-20h DWORD pointer to FAR routine to unlock region of file
call with BX = file handle
CX:DX = starting offset
SI:AX = size
Return: CF set on error
AL = DOS error code (21h) (see AH=59h)
Note: not called if file is marked as remote
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
-1Ch DWORD pointer to FAR routine to check if file region is locked
call with ES:DI -> system file table entry for file
CX = length of region from current position in file
Return: CF set if any portion of region locked
AX = 0021h
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
-18h DWORD pointer to FAR routine to get open file list entry
(called by AX=5D05h)
call with DS:SI -> DOS parameter list (see AX=5D00h)
DPL's BX = index of sharing record
DPL's CX = index of SFT in SFT chain of sharing rec
Return: CF set on error or not loaded
AX = DOS error code (12h) (see AH=59h)
CF clear if successful
ES:DI -> filename
CX = number of locks owned by specified SFT
BX = network machine number
DX destroyed
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
-14h DWORD pointer to FAR routine for updating FCB from SFT???
call with DS:SI -> unopened FCB
ES:DI -> system file table entry
Return: BL = C0h???
Note: copies following fields from SFT to FCB:
starting cluster of file 0Bh 1Ah
sharing record offset 33h 1Ch
file attribute 04h 1Eh
-10h DWORD pointer to FAR routine to get first cluster of FCB file ???
call with ES:DI -> system file table entry
DS:SI -> FCB
Return: CF set if SFT closed or sharing record offsets
mismatched
CF clear if successful
BX = starting cluster number from FCB
-0Ch DWORD pointer to FAR routine to close file if duplicate for process
DS:SI -> system file table
Return: AX = number of handle in JFT which already uses SFT
Note: called during open/create of a file
Note: SHARE assumes SS=DOS DS, directly accesses DOS internals
Note: if SFT was opened with inheritance enabled and sharing
mode 111, does something to all other SFTs owned by
same process which have the same file open mode and
sharing record
-08h DWORD pointer to FAR routine for ???
Note: SHARE assumes SS=DS=DOS DS, direct-accesses DOS internals
Note: closes various handles referring to file most-recently
opened
-04h DWORD pointer to FAR routine to update directory info in related SFT
entries
call with ES:DI -> system file table entry for file (see below)
AX = subfunction (apply to each related SFT)
00h: update time stamp (offset 0Dh) and date
stamp (offset 0Fh)
01h: update file size (offset 11h) and starting
cluster (offset 0Bh). Sets last-accessed
cluster fields to start of file if file
never accessed
02h: as function 01h, but last-accessed fields
always changed
03h: do both functions 00h and 02h
Note: follows ptr at offset 2Bh in system file table entries
Note: NOP if opened with no-inherit or via FCB
Format of sharing record:
Offset Size Description
00h BYTE flag
00h free block
01h allocated block
FFh end marker
01h WORD size of block
03h BYTE checksum of pathname (including NUL)
if sum of ASCII values is N, checksum is (N/256 + N%256)
04h WORD offset in SHARE's DS of lock record (see below)
06h DWORD pointer to start of system file table chain for file
0Ah WORD unique sequence number
0Ch var ASCIZ full pathname
Format of SHARE.EXE lock record:
Offset Size Description
00h WORD offset in SHARE's DS of next lock table in list
02h DWORD offset in file of start of locked region
06h DWORD offset in file of end of locked region
0Ah DWORD pointer to System File Table entry for this file
0Eh WORD PSP segment of lock's owner
Format of DOS 2.x system file tables:
Offset Size Description
00h DWORD pointer to next file table (offset FFFFh if last)
04h WORD number of files in this table
06h 28h bytes per file
Offset Size Description
00h BYTE number of file handles referring to this file
01h BYTE file open mode (see AH=3Dh)
02h BYTE file attribute
03h BYTE drive (0 = character device, 1 = A, 2 = B, etc)
04h 11 BYTEs filename in FCB format (no path,no period,blank-padded)
0Fh WORD ???
11h WORD ???
13h DWORD file size???
17h WORD file date in packed format (see AX=5700h)
19h WORD file time in packed format (see AX=5700h)
1Bh BYTE device attribute (see AX=4400h)
---character device---
1Ch DWORD pointer to device driver
---block device---
1Ch WORD starting cluster of file
1Eh WORD relative cluster in file of last cluster accessed
------
20h WORD absolute cluster number of current cluster
22h WORD ???
24h DWORD current file position???
Format of DOS 3.0 system file tables and FCB tables:
Offset Size Description
00h DWORD pointer to next file table (offset FFFFh if last)
04h WORD number of files in this table
06h 38h bytes per file
Offset Size Description
00h-1Eh as for DOS 3.1+ (see below)
1Fh WORD byte offset of directory entry within sector
21h 11 BYTES filename in FCB format (no path/period, blank-padded)
2Ch DWORD (SHARE.EXE) pointer to previous SFT sharing same file
30h WORD (SHARE.EXE) ??? network machine number
32h WORD PSP segment of file's owner (first three entries for
AUX/CON/PRN contain segment of IO.SYS startup code)
34h WORD (SHARE.EXE) offset in SHARE code seg of share record
36h WORD ??? apparently always 0000h
Format of DOS 3.1-3.3x system file tables and FCB tables:
Offset Size Description
00h DWORD pointer to next file table (offset FFFFh if last)
04h WORD number of files in this table
06h 35h bytes per file
Offset Size Description
00h WORD number of file handles referring to this file
02h WORD file open mode (see AH=3Dh)
bit 15 set if this file opened via FCB
04h BYTE file attribute (see AX=4301h)
05h WORD device info word (see AX=4400h)
bit 15 set if remote file
bit 14 set means do not set file date/time on closing
bit 12 set means don't inherit on EXEC
bits 5-0 drive number for disk files
07h DWORD pointer to device driver header if character device
else pointer to DOS Drive Parameter Block (see AH=32h)
0Bh WORD starting cluster of file
0Dh WORD file time in packed format (see AX=5700h)
0Fh WORD file date in packed format (see AX=5700h)
11h DWORD file size
---system file table---
15h DWORD current offset in file (may be larger than size of
file; INT 21/AH=42h does not check new position)
---FCB table---
15h WORD counter for last I/O to FCB
17h WORD counter for last open of FCB
(these are separate to determine the times of the
latest I/O and open)
---
19h WORD relative cluster within file of last cluster accessed
1Bh WORD absolute cluster number of last cluster accessed
0000h if file never read or written???
1Dh WORD number of sector containing directory entry
1Fh BYTE number of dir entry within sector (byte offset/32)
20h 11 BYTEs filename in FCB format (no path/period, blank-padded)
2Bh DWORD (SHARE.EXE) pointer to previous SFT sharing same file
2Fh WORD (SHARE.EXE) network machine number which opened file
31h WORD PSP segment of file's owner (see AH=26h) (first three
entries for AUX/CON/PRN contain segment of IO.SYS
startup code)
33h WORD offset within SHARE.EXE code segment of
sharing record (see above) 0000h = none
Format of DOS 4.0-5.0 system file tables and FCB tables:
Offset Size Description
00h DWORD pointer to next file table (offset FFFFh if last)
04h WORD number of files in this table
06h 3Bh bytes per file
Offset Size Description
00h WORD number of file handles referring to this file
02h WORD file open mode (see AH=3Dh)
bit 15 set if this file opened via FCB
04h BYTE file attribute (see AX=4301h)
05h WORD device info word (see AX=4400h)
bit 15 set if remote file
bit 14 set means do not set file date/time on closing
bit 13 set if named pipe
bit 12 set if no inherit
bit 11 set if network spooler
07h DWORD pointer to device driver header if character device
else pointer to DOS Drive Parameter Block (see AH=32h)
or REDIR data
0Bh WORD starting cluster of file
0Dh WORD file time in packed format (see AX=5700h)
0Fh WORD file date in packed format (see AX=5700h)
11h DWORD file size
15h DWORD current offset in file
---local file---
19h WORD relative cluster within file of last cluster accessed
1Bh DWORD number of sector containing directory entry
1Fh BYTE number of dir entry within sector (byte offset/32)
---network redirector---
19h DWORD pointer to REDIRIFS record
1Dh 3 BYTEs ???
------
20h 11 BYTEs filename in FCB format (no path/period, blank-padded)
2Bh DWORD (SHARE.EXE) pointer to previous SFT sharing same file
2Fh WORD (SHARE.EXE) network machine number which opened file
31h WORD PSP segment of file's owner (see AH=26h) (first three
entries for AUX/CON/PRN contain segment of IO.SYS
startup code)
33h WORD offset within SHARE.EXE code segment of
sharing record (see above) 0000h = none
35h WORD (local) absolute cluster number of last clustr accessed
(redirector) ???
37h DWORD pointer to IFS driver for file, 0000000h if native DOS
Format of current directory structure (CDS) (array, LASTDRIVE entries):
Offset Size Description
00h 67 BYTEs ASCIZ path in form X:\PATH (local) or \\MACH\PATH (network)
43h WORD drive attributes (see also note below and AX=5F07h)
bit 15: uses network redirector \ invalid if 00, installable
14: physical drive / file system if 11
13: JOIN'ed \ path above is true path that would be
12: SUBST'ed / needed if not under SUBST or JOIN
45h DWORD pointer to Drive Parameter Block for drive (see AH=32h)
---local drives---
49h WORD starting cluster of current directory
0000h = root, FFFFh = never accessed
4Bh WORD ??? seems to be FFFFh always
4Dh WORD ??? seems to be FFFFh always
---network drives---
49h DWORD pointer to redirector or REDIRIFS record, or FFFFh:FFFFh
4Dh WORD stored user data from INT 21/AX=5F03h???
------
4Fh WORD offset in current directory path of backslash corresponding to
root directory for drive
this value specifies how many characters to hide from the
"CHDIR" and "GETDIR" calls; normally set to 2 to hide the
drive letter and colon, SUBST, JOIN, and networks change it
so that only the appropriate portion of the true path is
visible to the user
---DOS 4.x---
51h BYTE ??? used by network
52h DWORD pointer to IFS driver for this drive, 00000000h if native DOS
56h WORD ???
Notes: the path for invalid drives is normally set to X:\, but may be empty
after JOIN x: /D in DR-DOS 5.0 or NET USE x: /D in older LAN versions
normally, only one of bits 13&12 may be set together with bit 14, but
DR-DOS 5.0 uses other combinations for bits 15-12: 0111 JOIN,
0001 SUBST, 0101 ASSIGN
Format of DR-DOS 5.0-6.0 current directory structure entry (array):
Offset Size Description
00h 67 BYTEs ASCIZ pathname of actual root directory for this logical drive
43h WORD drive attributes
1000h SUBSTed drive
3000h??? JOINed drive
4000h physical drive
5000h ASSIGNed drive
7000h JOINed drive
8000h network drive
45h BYTE physical drive number (0=A:) if this logical drive is valid
46h BYTE ??? apparently flags for JOIN and ASSIGN
47h WORD cluster number of start of parent directory (0000h = root)
49h WORD entry number of current directory in parent directory
4Bh WORD cluster number of start of current directory
4Dh 2 BYTEs used for media change detection (details not available)
4Fh WORD cluster number of SUBST/JOIN "root" directory
0000h if physical root directory
Format of device driver header:
Offset Size Description
00h DWORD pointer to next driver, offset=FFFFh if last driver
04h WORD device attributes
Character device:
bit 15 set
bit 14 IOCTL supported (see AH=44h)
bit 13 (DOS 3+) output until busy supported
bit 12 reserved
bit 11 (DOS 3+) OPEN/CLOSE/RemMedia calls supported
bits 10-8 reserved
bit 7 (DOS 5+) Generic IOCTL check call supported (cmd 19h)
(see AX=4410h,AX=4411h)
bit 6 (DOS 3.2+) Generic IOCTL call supported (command 13h)
(see AX=440Ch,AX=440Dh)
bit 5 reserved
bit 4 device is special (use INT 29 "fast console output")
bit 3 device is CLOCK$ (all reads/writes use transfer
record described below)
bit 2 device is NUL
bit 1 device is standard output
bit 0 device is standard input
Block device:
bit 15 clear
bit 14 IOCTL supported
bit 13 non-IBM format
bit 12 reserved
bit 11 (DOS 3+) OPEN/CLOSE/RemMedia calls supported
bit 10 reserved
bit 9 direct I/O not allowed???
(set by DOS 3.3 DRIVER.SYS for "new" drives)
bit 8 ??? set by DOS 3.3 DRIVER.SYS for "new" drives
bit 7 (DOS 5+) Generic IOCTL check call supported (cmd 19h)
(see AX=4410h,AX=4411h)
bit 6 (DOS 3.2+) Generic IOCTL call supported (command 13h)
implies support for commands 17h and 18h
(see AX=440Ch,AX=440Dh,AX=440Eh,AX=440Fh)
bits 5-2 reserved
bit 1 driver supports 32-bit sector addressing
bit 0 reserved
Note: for European MSDOS 4.0, bit 11 also indicates that bits
8-6 contain a version code (000 = DOS 3.0,3.1;
001 = DOS 3.2, 010 = European DOS 4.0)
06h WORD device strategy entry point
call with ES:BX -> request header (see INT 2F/AX=0802h)
08h WORD device interrupt entry point
---character device---
0Ah 8 BYTEs blank-padded character device name
---block device---
0Ah BYTE number of subunits (drives) supported by driver
0Bh 7 BYTEs unused
---
12h WORD (CD-ROM driver) reserved, must be 0000h
14h BYTE (CD-ROM driver) drive letter (must initially be 00h)
15h BYTE (CD-ROM driver) number of units
16h 6 BYTEs (CD-ROM driver) signature 'MSCDnn' where 'nn' is version
(currently '00')
Format of CLOCK$ transfer record:
Offset Size Description
00h WORD number of days since 1-Jan-1980
02h BYTE minutes
03h BYTE hours
04h BYTE hundredths of second
05h BYTE seconds
Format of DOS 2.x disk buffer:
Offset Size Description
00h DWORD pointer to next disk buffer, offset = FFFFh if last
least-recently used buffer is first in chain
04h BYTE drive (0=A, 1=B, etc), FFh if not in use
05h 3 BYTEs unused??? (seems always to be 00h 00h 01h)
08h WORD logical sector number
0Ah BYTE number of copies to write (1 for non-FAT sectors)
0Bh BYTE sector offset between copies if multiple copies to be written
0Ch DWORD pointer to DOS Drive Parameter Block (see AH=32h)
10h buffered data
Format of DOS 3.x disk buffer:
Offset Size Description
00h DWORD pointer to next disk buffer, offset = FFFFh if last
least-recently used buffer is first in chain
04h BYTE drive (0=A,1=B, etc), FFh if not in use
05h BYTE flags
bit 7: ???
bit 6: buffer dirty
bit 5: buffer has been referenced
bit 4: ???
bit 3: sector in data area
bit 2: sector in a directory, either root or subdirectory
bit 1: sector in FAT
bit 0: boot sector??? (guess)
06h WORD logical sector number
08h BYTE number of copies to write (1 for non-FAT sectors)
09h BYTE sector offset between copies if multiple copies to be written
0Ah DWORD pointer to DOS Drive Parameter Block (see AH=32h)
0Eh WORD unused??? (almost always 0)
10h buffered data
Format of DOS 4.00 (pre UR 25066) disk buffer info:
Offset Size Description
00h DWORD pointer to array of disk buffer hash chain heads (see below)
04h WORD number of disk buffer hash chains (referred to as NDBCH below)
06h DWORD pointer to lookahead buffer, zero if not present
0Ah WORD number of lookahead sectors, else zero (the y in BUFFERS=x,y)
0Ch BYTE 00h if buffers in EMS (/X), FFh if not
0Dh WORD EMS handle for buffers, zero if not in EMS
0Fh WORD EMS physical page number used for buffers (usually 255)
11h WORD ??? seems always to be 0001h
13h WORD segment of EMS physical page frame
15h WORD ??? seems always to be zero
17h 4 WORDs EMS partial page mapping information???
Format of DOS 4.01 (from UR 25066 Corrctive Services Disk on) disk buffer info:
Offset Size Description
00h DWORD pointer to array of disk buffer hash chain heads (see below)
04h WORD number of disk buffer hash chains (referred to as NDBCH below)
06h DWORD pointer to lookahead buffer, zero if not present
0Ah WORD number of lookahead sectors, else zero (the y in BUFFERS=x,y)
0Ch BYTE 01h, possibly to distinguish from pre-UR 25066 format
0Dh WORD ??? EMS segment for BUFFERS (only with /XD)
0Fh WORD ??? EMS physical page number of EMS seg above (only with /XD)
11h WORD ??? EMS segment for ??? (only with /XD)
13h WORD ??? EMS physical page number of above (only with /XD)
15h BYTE ??? number of EMS page frames present (only with /XD)
16h WORD segment of one-sector workspace buffer allocated in main memory
if BUFFERS/XS or /XD options in effect, possibly to avoid DMA
into EMS
18h WORD EMS handle for buffers, zero if not in EMS
1Ah WORD EMS physical page number used for buffers (usually 255)
1Ch WORD ??? appears always to be 0001h
1Eh WORD segment of EMS physical page frame
20h WORD ??? appears always to be zero
22h BYTE 00h if /XS, 01h if /XD, FFh if BUFFERS not in EMS
Format of DOS 4.x disk buffer hash chain head (array, one entry per chain):
Offset Size Description
00h WORD EMS logical page number in which chain is resident, -1 if not
in EMS
02h DWORD pointer to least recently used buffer header. All buffers on
this chain are in the same segment.
06h BYTE number of dirty buffers on this chain
07h BYTE reserved (00h)
Notes: buffered disk sectors are assigned to chain N where N is the sector's
address modulo NDBCH, 0 <= N <= NDBCH-1
each chain resides completely within one EMS page
this structure is in main memory even if buffers are in EMS
Format of DOS 4.0-5.0 disk buffer:
Offset Size Description
00h WORD forward ptr, offset only, to next least recently used buffer
02h WORD backward ptr, offset only
04h BYTE drive (0=A,1=B, etc), FFh if not in use
05h BYTE flags
bit 7: remote buffer
bit 6: buffer dirty
bit 5: buffer has been referenced
bit 4: search data buffer (only valid if remote buffer)
bit 3: sector in data area
bit 2: sector in a directory, either root or subdirectory
bit 1: sector in FAT
bit 0: reserved
06h DWORD logical sector number
0Ah BYTE number of copies to write
for FAT sectors, same as number of FATs
for data and directory sectors, usually 1
0Bh WORD offset in sectors between copies to write for FAT sectors
0Dh DWORD pointer to DOS Drive Parameter Block (see AH=32h)
11h WORD buffer use count if remote buffer (see flags above)
13h BYTE reserved
14h buffered data
Note: for DOS 4.x, all buffered sectors which have the same hash value
(computed as the sum of high and low words of the logical sector
number divided by NDBCH) are on the same doubly-linked circular
chain; for DOS 5.0, only a single circular chain exists.
the links consist of offset addresses only, the segment being the same
for all buffers in the chain.
Format of DOS 5.0 disk buffer info:
Offset Size Description
00h DWORD pointer to least-recently-used buffer header (may be in HMA)
(see above)
04h WORD 0000h (DOS 5 does not hash disk buffers, so offset 00h points
directly at the only buffer chain)
06h DWORD pointer to lookahead buffer, zero if not present
0Ah WORD number of lookahead sectors, else zero (the y in BUFFERS=x,y)
0Ch BYTE buffer location
00h base memory, no workspace buffer
01h HMA, workspace buffer in base memory
0Dh DWORD pointer to one-segment workspace buffer in base memory
11h 3 BYTEs unused???
14h WORD ???
16h BYTE ??? apparently always 00h
17h BYTE ??? apparently always FFh
18h BYTE ??? apparently always 00h
19h BYTE ??? apparently always 00h
1Ah WORD ??? segment within HIMEM.SYS area when buffers are in HMA and
UMBs are enabled???, else 0000h
1Ch BYTE bit 0 set iff UMB MCB chain linked to normal MCB chain
1Dh WORD ???
1Fh WORD segment of first MCB in upper memory blocks or FFFFh if DOS
memory chain in base 640K only (first UMB MCB usually at 9FFFh,
locking out video memory with a DOS-owned memory block)
21h WORD paragraph of start of most recent MCB chain search
Format of IFS driver list:
Offset Size Description
00h DWORD pointer to next driver header
04h 8 BYTEs IFS driver name (blank padded), as used by FILESYS command
0Ch 4 BYTEs ???
10h DWORD pointer to IFS utility function entry point (see below)
call with ES:BX -> IFS request (see below)
14h WORD offset in header's segment of driver entry point
???
Call IFS utility function entry point with:
AH = 20h miscellaneous functions
AL = 00h get date
Return: CX = year
DH = month
DL = day
AL = 01h get process ID and computer ID
Return: BX = current PSP segment
DX = active network machine number
AL = 05h get file system info
ES:DI -> 16-byte info buffer
Return: buffer filled
Offset Size Description
00h 2 BYTEs unused
02h WORD number of SFTs (actually counts only
the first two file table arrays)
04h WORD number of FCB table entries
06h WORD number of proctected FCBs
08h 6 BYTEs unused
0Eh WORD largest sector size supported
AL = 06h get machine name
ES:DI -> 18-byte buffer for name
Return: buffer filled with name starting at offset 02h
AL = 08h get sharing retry count
Return: BX = sharing retry count
AL = other
Return: CF set
AH = 21h get redirection state
BH = type (03h disk, 04h printer)
Return: BH = state (00h off, 01h on)
AH = 22h ??? some sort of time calculation
AL = 00h ???
nonzero ???
AH = 23h ??? some sort of time calculation
AH = 24h compare filenames
DS:SI -> first ASCIZ filename
ES:DI -> second ASCIZ filename
Return: ZF set if files are same ignoring case and / vs \
AH = 25h normalize filename
DS:SI -> ASCIZ filename
ES:DI -> buffer for result
Return: filename uppercased, forward slashes changed to backslashes
AH = 26h get DOS stack
Return: DS:SI -> top of stack
CX = size of stack in bytes
AH = 27h increment InDOS flag
AH = 28h decrement InDOS flag
Note: IFS drivers which do not wish to implement functions 20h or 24h-28h may
pass them on to the default handler pointed at by [LoL+37h]
Format of IFS request block:
Offset Size Description
00h WORD total size in bytes of request
02h BYTE class of request
02h ???
03h redirection
04h ???
05h file access
06h convert error code to string
07h ???
03h WORD returned DOS error code
05h BYTE IFS driver exit status
00h success
01h ???
02h ???
03h ???
04h ???
FFh internal failure
06h 16 BYTEs ???
---request class 02h---
16h BYTE function code
04h ???
17h BYTE unused???
18h DWORD pointer to ???
1Ch DWORD pointer to ???
20h 2 BYTEs ???
---request class 03h---
16h BYTE function code
17h BYTE ???
18h DWORD pointer to ???
1Ch DWORD pointer to ???
22h WORD returned ???
24h WORD returned ???
26h WORD returned ???
28h BYTE returned ???
29h BYTE unused???
---request class 04h---
16h DWORD pointer to ???
1Ah DWORD pointer to ???
---request class 05h---
16h BYTE function code
01h flush disk buffers
02h get disk space
03h MKDIR
04h RMDIR
05h CHDIR
06h delete file
07h rename file
08h search directory
09h file open/create
0Ah LSEEK
0Bh read from file
0Ch write to file
0Dh lock region of file
0Eh commit/close file
0Fh get/set file attributes
10h printer control
11h ???
12h process termination
13h ???
---class 05h function 01h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h 4 BYTEs ???
26h BYTE ???
27h BYTE ???
---class 05h function 02h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h 4 BYTEs ???
26h WORD returned total clusters
28h WORD returned sectors per cluster
2Ah WORD returned bytes per sector
2Ch WORD returned available clusters
2Eh BYTE returned ???
2Fh BYTE ???
---class 05h functions 03h,04h,05h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h 4 BYTEs ???
26h DWORD pointer to directory name
---class 05h function 06h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h 4 BYTEs ???
26h WORD attribute mask
28h DWORD pointer to filename
---class 05h function 07h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h 4 BYTEs ???
26h WORD attribute mask
28h DWORD pointer to source filespec
2Ch DWORD pointer to destination filespec
---class 05h function 08h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h 4 BYTEs ???
26h BYTE 00h FINDFIRST
01h FINDNEXT
28h DWORD pointer to FindFirst search data + 01h if FINDNEXT
2Ch WORD search attribute if FINDFIRST
2Eh DWORD pointer to filespec if FINDFIRST
---class 05h function 09h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h DWORD pointer to IFS open file structure (see below)
26h WORD ??? \ together, specify open vs. create, whether or
28h WORD ??? / not to truncate
2Ah 4 BYTEs ???
2Eh DWORD pointer to filename
32h 4 BYTEs ???
36h WORD file attributes on call
returned ???
38h WORD returned ???
---class 05h function 0Ah---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h DWORD pointer to IFS open file structure (see below)
26h BYTE seek type (02h = from end)
28h DWORD offset on call
returned new absolute position
---class 05h functions 0Bh,0Ch---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h DWORD pointer to IFS open file structure (see below)
28h WORD number of bytes to transfer
returned bytes actually transferred
2Ah DWORD transfer address
---class 05h function 0Dh---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h DWORD pointer to IFS open file structure (see below)
26h BYTE file handle???
27h BYTE unused???
28h WORD ???
2Ah WORD ???
2Ch WORD ???
2Eh WORD ???
---class 05h function 0Eh---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h DWORD pointer to IFS open file structure (see below)
26h BYTE 00h commit file
01h close file
27h BYTE unused???
---class 05h function 0Fh---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h 4 BYTEs ???
26h BYTE 02h GET attributes
03h PUT attributes
27h BYTE unused???
28h 12 BYTEs ???
34h WORD search attributes???
36h DWORD pointer to filename
3Ah WORD (GET) returned ???
3Ch WORD (GET) returned ???
3Eh WORD (GET) returned ???
40h WORD (GET) returned ???
42h WORD (PUT) new attributes
(GET) returned attributes
---class 05h function 10h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h DWORD pointer to IFS open file structure (see below)
26h WORD ???
28h DWORD pointer to ???
2Ch WORD ???
2Eh BYTE ???
2Fh BYTE subfunction
01h get printer setup
03h ???
04h ???
05h ???
06h ???
07h ???
21h set printer setup
---class 05h function 11h---
17h 7 BYTEs ???
1Eh DWORD pointer to ???
22h DWORD pointer to IFS open file structure (see below)
26h BYTE subfunction
27h BYTE unused???
28h WORD ???
2Ah WORD ???
2Ch WORD ???
2Eh BYTE ???
2Fh BYTE ???
---class 05h function 12h---
17h 15 BYTEs unused???
26h WORD PSP segment
28h BYTE type of process termination
29h BYTE unused???
---class 05h function 13h---
17h 15 BYTEs unused???
26h WORD PSP segment
---request class 06h---
16h DWORD returned pointer to string corresponding to error code at 03h
1Ah BYTE returned ???
1Bh BYTE unused
---request class 07h---
16h DWORD pointer to IFS open file structure (see below)
1Ah BYTE ???
1Bh BYTE unused???
Format of IFS open file structure:
Offset Size Description
00h WORD ???
02h WORD device info word
04h WORD file open mode
06h WORD ???
08h WORD file attributes
0Ah WORD owner's network machine number
0Ch WORD owner's PSP segment
0Eh DWORD file size
12h DWORD current offset in file
16h WORD file time
18h WORD file date
1Ah 11 BYTEs filename in FCB format
25h WORD ???
27h WORD hash value of SFT address
(low word of linear address + segment&F000h)
29h 3 WORDs network info from SFT
2Fh WORD ???
Format of one item in DOS 4+ list of special program names:
Offset Size Description
00h BYTE length of name (00h = end of list)
01h N BYTEs name in format name.ext
N 2 BYTEs DOS version to return for program (major,minor)
(see AH=30h,INT 2F/AX=122Fh)
---DOS 4 only---
N+2 BYTE number of times to return fake version number (FFh = always)
Note: if the name of the executable for the program making the DOS "get
version" call matches one of the names in this list, DOS returns the
specified version rather than the true version number
----------215252-----------------------------
INT 21 - VIRUS - "516"/"Leapfrog" - INSTALLATION CHECK
AX = 5252h
Return: BX = FFEEh if resident
SeeAlso: AX=4BFFh"Cascade",AX=58CCh
----------2153-------------------------------
INT 21 - DOS 2+ internal - TRANSLATE BIOS PARAMETER BLOCK TO DRIVE PARAM BLOCK
AH = 53h
DS:SI -> BIOS Parameter Block (see below)
ES:BP -> buffer for Drive Parameter Block (see AH=32h for format)
Return: ES:BP buffer filled
Note: for DOS 3+, the cluster at which to start searching is set to 0000h
and the number of free clusters is set to FFFFh (unknown)
Format of BIOS Parameter Block:
Offset Size Description
00h WORD number of bytes per sector
02h BYTE number of sectors per cluster
03h WORD number of reserved sectors at start of disk
05h BYTE number of FATs
06h WORD number of entries in root directory
08h WORD total number of sectors
for DOS 4+, set to zero if partition >32M, then set DWORD at
15h to actual number of sectors
0Ah BYTE media ID byte
0Bh WORD number of sectors per FAT
---DOS 3+---
0Dh WORD number of sectors per track
0Fh WORD number of heads
11h DWORD number of hidden sectors
15h 11 BYTEs reserved
---DOS 4+ ---
15h DWORD total number of sectors if word at 08h contains zero
19h 6 BYTEs ???
1Fh WORD number of cylinders
21h BYTE device type
22h WORD device attributes (removable or not, etc)
---European MSDOS 4.00---
15h DWORD total number of sectors if word at 08h contains zero
(however, this DOS does not actually implement >32M partitions)
----------2154-------------------------------
INT 21 - DOS 2+ - GET VERIFY FLAG
AH = 54h
Return: AL = verify flag
00h off
01h on (all disk writes verified after writing)
SeeAlso: AH=2Eh
----------2155-------------------------------
INT 21 - DOS 2+ internal - CREATE CHILD PSP
AH = 55h
DX = segment at which to create new PSP
SI = (DOS 3+) value to place in memory size field at DX:[0002h]
Return: CF clear if successful
Notes: creates a "child" PSP rather than making an exact copy of the current
PSP; the new PSP's parent pointer is set to the current PSP and the
reference count for each inherited file is incremented
(DOS 2+) sets current PSP to DX
(DOS 3+) marks "no inherit" file handles as closed in child PSP
SeeAlso: AH=26h,AH=50h
----------2156-------------------------------
INT 21 - DOS 2+ - "RENAME" - RENAME FILE
AH = 56h
DS:DX -> ASCIZ filename of existing file (no wildcards, but see below)
ES:DI -> ASCIZ new filename (no wildcards)
CL = attribute mask (server call only, see below)
Return: CF clear if successful
CF set on error
AX = error code (02h,03h,05h,11h) (see AH=59h)
Notes: allows move between directories on same logical volume
does not set the archive attribute (see AX=4300h), which results in
incremental backups not backing up the file under its new name
open files should not be renamed
(DOS 3+) allows renaming of directories
(DOS 3.1+) wildcards are allowed if invoked via AX=5D00h, in which case
error 12h (no more files) is returned on success, and both source and
destination specs must be canonical (as returned by AH=60h).
Wildcards in the destination are replaced by the corresponding char
of each source file being renamed. Under DOS 3.x, the call will fail
if the destination wildcard is *.* or equivalent. When invoked via
AX=5D00h, only those files matching the attribute mask in CL are
renamed.
under the FlashTek X-32 DOS extender, the old-name pointer is in DS:EDX
and the new-name pointer is in ES:EDI (DS must equal ES)
SeeAlso: AH=17h,AX=4301h,AH=60h,AX=5D00h
----------215700-----------------------------
INT 21 - DOS 2+ - GET FILE'S DATE AND TIME
AX = 5700h
BX = file handle
Return: CF clear if successful
CX = file's time
bits 15-11: hours (0-23)
10-5: minutes
4-0: seconds/2
DX = file's date
bits 15-9: year - 1980
8-5: month
4-0: day
CF set on error
AX = error code (01h,06h) (see AH=59h)
SeeAlso: AX=5701h
----------215701-----------------------------
INT 21 - DOS 2+ - SET FILE'S DATE AND TIME
AX = 5701h
BX = file handle
CX = new time (see AX=5700h)
DX = new date (see AX=5700h)
Return: CF clear if successful
CF set on error
AX = error code (01h,06h) (see AH=59h)
SeeAlso: AX=5700h
----------215702-----------------------------
INT 21 - DOS 4.x only - GET ???
AX = 5702h
BX = ??? (0000h through 0004h)
DS:SI -> ???
ES:DI -> result buffer
CX = size of result buffer
Return: CX = size of returned data
SeeAlso: AX=5703h,AX=5704h
----------215703-----------------------------
INT 21 - DOS 4.x only - GET ???
AX = 5703h
BX = file handle (only 0000h through 0004h valid)
DS:SI -> ??? passed through to INT 2F/AX=112Dh
ES:DI -> result buffer
CX = size of result buffer
Return: CX = size of returned data
ES:DI -> zero word (DOS 4.0) if CX >= 2 on entry
SeeAlso: AX=5702h,AX=5704h,INT 2F/AX=112Dh
----------215704-----------------------------
INT 21 - DOS 4.x only - TRUNCATE OPEN FILE TO ZERO LENGTH
AX = 5704h
BX = file handle (only 0000h through 0004h valid)
DS:SI -> ??? passed through to INT 2F/AX=112Dh
ES:DI -> result buffer
CX = size of result buffer
Return: CX = size of returned data
ES:DI -> zero word (DOS 4.0) if CX >= 2 on entry
SeeAlso: AX=5702h,AX=5703h,INT 2F/AX=112Dh
----------2158-------------------------------
INT 21 - DOS 3+ - GET OR SET MEMORY ALLOCATION STRATEGY
AH = 58h
AL = subfunction
00h get allocation strategy
Return: AX = current strategy
00h low memory first fit
01h low memory best fit
02h low memory last fit
---DOS 5.0---
40h high memory first fit
41h high memory best fit
42h high memory last fit
80h first fit, try high then low memory
81h best fit, try high then low memory
82h last fit, try high then low memory
01h set allocation strategy
BL = new allocation strategy (see above)
BH = 00h (DOS 5.0)
Return: CF clear if successful
CF set on error
AX = error code (01h) (see AH=59h)
Notes: the Set subfunction accepts any value in BL for DOS 3.x and 4.x;
2 or greater means last fit
the Get subfunction returns the last value set
a program which changes the allocation strategy should restore it
before terminating
Toshiba MSDOS 2.11 supports subfunctions 00h and 01h
DR-DOS 3.41 reportedly reverses subfunctions 00h and 01h
SeeAlso: AH=48h,AH=49h,AH=4Ah,INT 2F/AX=4310h,INT 67/AH=3Fh
----------2158-------------------------------
INT 21 - DOS 5.0 - GET OR SET UMB LINK STATE
AH = 58h
AL = subfunction
02h get UMB link state
Return: AL = 00h UMBs not part of DOS memory chain
= 01h UMBs in DOS memory chain
03h set UMB link state
BX = 0000h remove UMBs from DOS memory chain
= 0001h add UMBs to DOS memory chain
Return: CF clear if successful
CF set on error
AX = error code (01h) (see AH=59h)
Note: a program which changes the UMB link state should restore it before
terminating
----------2158CC-----------------------------
INT 21 - VIRUS - "1067"/"Headcrash" - INSTALLATION CHECK
AX = 58CCh
Return: CF clear if resident
SeeAlso: AX=5252h,AX=6969h
----------2159--BX0000-----------------------
INT 21 - DOS 3+ - GET EXTENDED ERROR INFORMATION
AH = 59h
BX = 0000h
Return: AX = extended error code (see below)
BH = error class (see below)
BL = recommended action (see below)
CH = error locus (see below)
ES:DI may be pointer (see error code list below)
CL, DX, SI, BP, and DS destroyed
Notes: functions available under DOS 2.x map the true DOS 3+ error code into
one supported under DOS 2.x
you should call this function to retrieve the true error code when an
FCB or DOS 2.x call returns an error
SeeAlso: AX=5D0Ah,INT 2F/AX=122Dh
Values for extended error code:
00h no error
01h function number invalid
02h file not found
03h path not found
04h too many open files (no handles available)
05h access denied
06h invalid handle
07h memory control block destroyed
08h insufficient memory
09h memory block address invalid
0Ah environment invalid (usually >32K in length)
0Bh format invalid
0Ch access code invalid
0Dh data invalid
0Eh reserved
0Fh invalid drive
10h attempted to remove current directory
11h not same device
12h no more files
---DOS 3+---
13h disk write-protected
14h unknown unit
15h drive not ready
16h unknown command
17h data error (CRC)
18h bad request structure length
19h seek error
1Ah unknown media type (non-DOS disk)
1Bh sector not found
1Ch printer out of paper
1Dh write fault
1Eh read fault
1Fh general failure
20h sharing violation
21h lock violation
22h disk change invalid
ES:DI -> ASCIZ volume label of required disk
23h FCB unavailable
24h sharing buffer overflow
25h (DOS 4+) code page mismatch
26h (DOS 4+) cannot complete file operation (out of input)
27h (DOS 4+) insufficient disk space
28h-31h reserved
32h network request not supported
33h remote computer not listening
34h duplicate name on network
35h network name not found
36h network busy
37h network device no longer exists
38h network BIOS command limit exceeded
39h network adapter hardware error
3Ah incorrect response from network
3Bh unexpected network error
3Ch incompatible remote adapter
3Dh print queue full
3Eh queue not full
3Fh not enough space to print file
40h network name was deleted
41h network: Access denied
42h network device type incorrect
43h network name not found
44h network name limit exceeded
45h network BIOS session limit exceeded
46h temporarily paused
47h network request not accepted
48h network print/disk redirection paused
49h (LANtastic) invalid network version
4Ah (LANtastic) account expired
4Bh (LANtastic) password expired
4Ch (LANtastic) login attempt invalid at this time
4Dh (LANtastic v3+) disk limit exceeded on network node
4Eh (LANtastic v3+) not logged in to network node
4Fh reserved
50h file exists
51h reserved
52h cannot make directory
53h fail on INT 24h
54h (DOS 3.3+) too many redirections
55h (DOS 3.3+) duplicate redirection
56h (DOS 3.3+) invalid password
57h (DOS 3.3+) invalid parameter
58h (DOS 3.3+) network write fault
59h (DOS 4+) function not supported on network
5Ah (DOS 4+) required system component not installed
Values for Error Class:
01h out of resource (storage space or I/O channels)
02h temporary situation (file or record lock)
03h authorization (denied access)
04h internal (system software bug)
05h hardware failure
06h system failure (configuration file missing or incorrect)
07h application program error
08h not found
09h bad format
0Ah locked
0Bh media error
0Ch already exists
0Dh unknown
Values for Suggested Action:
01h retry
02h delayed retry
03h prompt user to reenter input
04h abort after cleanup
05h immediate abort
06h ignore
07h retry after user intervention
Values for Error Locus:
01h unknown or not appropriate
02h block device (disk error)
03h network related
04h serial device (timeout)
05h memory related
----------2159--BX0001-----------------------
INT 21 - European MSDOS 4.0 - GET HARD ERROR INFORMATION
AH = 59h
BX = 0001h
Return: ES:DI -> hard error information packet (see below) for most recent
hard (critical) error
SeeAlso: AH=95h,INT 24
Format of hard error information packet:
Offset Size Description
00h WORD contents of AX at system entry
02h WORD Process ID which encountered error
04h WORD contents of AX at time of error
06h BYTE error type
00h physical I/O error
01h disk change request
02h file sharing violation
03h FCB problem
04h file locking violation
05h bad FAT
06h network detected error
07h BYTE INT 24 error code
08h WORD extended error code (see AH=59h/BX=0000h)
0Ah DWORD pointer to associated device
----------215A-------------------------------
INT 21 - DOS 3+ - CREATE TEMPORARY FILE
AH = 5Ah
CX = file attribute (see AX=4301h)
DS:DX -> ASCIZ path ending with a '\' + 13 zero bytes to receive the
generated filename
Return: CF clear if successful
AX = file handle opened for read/write in compatibility mode
DS:DX pathname extended with generated name for temporary file
CF set on error
AX = error code (03h,04h,05h) (see AH=59h)
Notes: creates a file with a unique name which must be explicitly deleted
COMPAQ DOS 3.31 hangs if the pathname is at XXXXh:0000h; it apparently
wraps around to the end of the segment
under the FlashTek X-32 DOS extender, the path pointer is in DS:EDX
SeeAlso: AH=3Ch,AH=5Bh
----------215B-------------------------------
INT 21 - DOS 3+ - CREATE NEW FILE
AH = 5Bh
CX = file attribute (see AX=4301h)
DS:DX -> ASCIZ filename
Return: CF clear if successful
AX = file handle opened for read/write in compatibility mode
CF set on error
AX = error code (03h,04h,05h,50h) (see AH=59h)
Notes: unlike AH=3Ch, this function will fail if the specified file exists
rather than truncating it; this permits its use in creating semaphore
files because it is an atomic "test and set" operation
under the FlashTek X-32 DOS extender, the filename pointer is in DS:EDX
SeeAlso: AH=3Ch,AH=5Ah
----------215C-------------------------------
INT 21 - DOS 3+ - "FLOCK" - RECORD LOCKING
AH = 5Ch
AL = subfunction
00h lock region of file
01h unlock region of file
BX = file handle
CX:DX = start offset of region within file
SI:DI = length of region in bytes
Return: CF clear if successful
CF set on error
AX = error code (01h,06h,21h,24h) (see AH=59h)
Notes: error returned unless SHARE or network installed
an unlock call must specify the same region as some prior lock call
locked regions become entirely inaccessible to other processes
duplicate handles created with AH=45h or AH=46h inherit locks, but
handles inherited by child processes (see AH=4Bh) do not
SeeAlso: AX=440Bh,AH=BCh,AH=BEh,INT 2F/AX=110Ah,INT 2F/AX=110Bh
----------215D00-----------------------------
INT 21 U - DOS 3.1+ internal - SERVER FUNCTION CALL
AX = 5D00h
DS:DX -> DOS parameter list (see below)
DPL contains all register values for a call to INT 21h
Return: as appropriate for function being called
Notes: does not check AH. Out of range values will crash the system
executes using specified computer ID and process ID
sharing delay loops skipped
a special sharing mode is enabled
wildcards are enabled for DELETE (AH=41h) and RENAME (AH=56h)
an extra file attribute parameter is enabled for OPEN (AH=3Dh),
DELETE (AH=41h), and RENAME (AH=56h)
functions which take filenames require canonical names (as returned
by AH=60h); this is apparently to prevent multi-hop file forwarding
SeeAlso: AH=3Dh,AH=41h,AH=56h,AH=60h
Format of DOS parameter list:
Offset Size Description
00h WORD AX
02h WORD BX
04h WORD CX
06h WORD DX
08h WORD SI
0Ah WORD DI
0Ch WORD DS
0Eh WORD ES
10h WORD reserved (0)
12h WORD computer ID (0 = current system)
14h WORD process ID (PSP segment on specified computer)
----------215D01-----------------------------
INT 21 U - DOS 3.1+ internal - COMMIT ALL FILES FOR SPECIFIED COMPUTER/PROCESS
AX = 5D01h
DS:DX -> DOS parameter list (see AX=5D00h), only computer ID and
process ID fields used
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Notes: flushes buffers and updates directory entries for each file which has
been written to; if remote file, calls INT 2F/AX=1107h
the computer ID and process ID are stored but ignored under DOS 3.3
SeeAlso: AH=0Dh,AH=68h,INT 2F/AX=1107h
----------215D02-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - CLOSE FILE BY NAME
AX = 5D02h
DS:DX -> DOS parameter list (see AX=5D00h), only fields DX, DS,
computer ID, and process ID used
DPL's DS:DX -> ASCIZ name of file to close
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Notes: error unless SHARE is loaded (calls [SysFileTable-28h]) (see AH=52h)
name must be canonical fully-qualified, such as returned by AH=60h
SeeAlso: AX=5D03h,AX=5D04h,AH=3Eh,AH=60h
----------215D03-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - CLOSE ALL FILES FOR GIVEN COMPUTER
AX = 5D03h
DS:DX -> DOS parameter list (see AX=5D00h), only computer ID used
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: error unless SHARE is loaded (calls [SysFileTable-30h]) (see AH=52h)
SeeAlso: AX=5D02h,AX=5D04h
----------215D04-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - CLOSE ALL FILES FOR GIVEN PROCESS
AX = 5D04h
DS:DX -> DOS parameter list (see AX=5D00h), only computer ID and
process ID fields used
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: error unless SHARE is loaded (calls [SysFileTable-2Ch]) (see AH=52h)
SeeAlso: AX=5D02h,AX=5D03h,INT 2F/AX=111Dh
----------215D05-----------------------------
INT 21 U - DOS 3.1+ internal - SHARE.EXE - GET OPEN FILE LIST ENTRY
AX = 5D05h
DS:DX -> DOS parameter list (see AX=5D00h)
DPL's BX = index of sharing record (see AH=52h)
DPL's CX = index of SFT in sharing record's SFT list
Return: CF clear if successful
ES:DI -> ASCIZ filename
BX = network machine number of SFT's owner
CX = number of locks held by SFT's owner
CF set if either index out of range
AX = 0012h (no more files)
Notes: error unless SHARE is loaded (calls [SysFileTable-18h]) (see AH=52h)
names are always canonical fully-qualified, such as returned by AH=60h
SeeAlso: AH=5Ch,AH=60h
----------215D06-----------------------------
INT 21 U - DOS 3.0+ internal - GET ADDRESS OF DOS SWAPPABLE DATA AREA
AX = 5D06h
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
DS:SI -> nonreentrant data area (includes all three DOS stacks)
(critical error flag is first byte)
CX = size in bytes of area which must be swapped while in DOS
DX = size in bytes of area which must always be swapped
Notes: the Critical Error flag is used in conjunction with the InDOS flag
(see AH=34h) to determine when it is safe to enter DOS from a TSR
setting CritErr flag allows use of functions 50h/51h from INT 28h under
DOS 2.x by forcing use of correct stack
swapping the data area allows reentering DOS unless DOS is in a
critical section delimited by INT 2A/AH=80h and INT 2A/AH=81h,82h
under DOS 4.0, AX=5D0Bh should be used instead of this function
SeeAlso: AX=5D0Bh,INT 2A/AH=80h,INT 2A/AH=81h,INT 2A/AH=82h
Format of DOS 3.10-3.30 Swappable Data Area:
Offset Size Description
00h BYTE critical error flag
01h BYTE InDOS flag (count of active INT 21 calls)
02h BYTE drive on which current critical error occurred, or FFh
03h BYTE locus of last error
04h WORD extended error code of last error
06h BYTE suggested action for last error
07h BYTE class of last error
08h DWORD ES:DI pointer for last error
0Ch DWORD current DTA
10h WORD current PSP
12h WORD stores SP across an INT 23
14h WORD return code from last process termination (zerod after reading
with AH=4Dh)
16h BYTE current drive
17h BYTE extended break flag
---remainder need only be swapped if in DOS---
18h WORD value of AX on call to INT 21
1Ah WORD PSP segment for sharing/network
1Ch WORD network machine number for sharing/network (0000h = us)
1Eh WORD first usable memory block found when allocating memory
20h WORD best usable memory block found when allocating memory
22h WORD last usable memory block found when allocating memory
24h WORD memory size in paragraphs (used only during initialization)
26h WORD ???
28h BYTE INT 24 returned Fail
29h BYTE bit flags for allowable actions on INT 24
2Ah BYTE ??? flag
2Bh BYTE FFh if Ctrl-Break termination, 00h otherwise
2Ch BYTE ??? flag of some kind
2Dh BYTE ??? (doesn't seem to be referenced)
2Eh BYTE day of month
2Fh BYTE month
30h WORD year - 1980
32h WORD number of days since 1-1-1980
34h BYTE day of week (0 = Sunday)
35h BYTE working SFT pointer at SDA+2AAh is valid ???
36h BYTE safe to call INT 28 if nonzero
37h BYTE flag: if nonzero, INT 24 abort turned into INT 24 fail
(set only during process termination)
38h 26 BYTEs device driver request header (see INT 2F/AX=0802h)
52h DWORD pointer to device driver entry point (used in calling driver)
56h 22 BYTEs device driver request header
6Ch 22 BYTEs device driver request header
82h BYTE type of PSP copy (00h=simple for INT 21/AH=26h, FFh=make child)
83h BYTE ??? apparently not referenced by kernel
84h 3 BYTEs 24-bit user number (see AH=30h)
87h BYTE OEM number (see AH=30h)
88h 2 BYTEs ???
8Ah 6 BYTEs CLOCK$ transfer record (see AH=52h)
90h BYTE ??? buffer for single-byte I/O functions
91h BYTE ??? apparently not referenced by kernel
92h 128 BYTEs buffer for filename
112h 128 BYTEs buffer for filename
192h 21 BYTEs findfirst/findnext search data block (see AH=4Eh)
1A7h 32 BYTEs directory entry for found file
1C7h 81 BYTEs copy of current directory structure for drive being accessed
218h 11 BYTEs FCB-format filename for device name comparison
223h BYTE unused???
224h 11 BYTEs wildcard destination specification for rename (FCB format)
22Fh 2 BYTEs ???
231h WORD ???
233h 5 BYTEs ???
238h BYTE extended FCB file attribute
239h BYTE type of FCB (00h regular, FFh extended)
23Ah BYTE directory search attributes
23Bh BYTE file open mode???
23Ch BYTE ??? flag bits 0 and 4
23Dh BYTE ??? flag or counter
23Eh BYTE ??? flag
23Fh BYTE flag indicating how DOS function was invoked
(00h = direct INT 20/INT 21, FFh = server call AX=5D00h)
240h BYTE ???
241h BYTE ??? flag
242h BYTE flag: 00h if read, 01h if write
243h BYTE drive number for ???
244h BYTE ???
245h BYTE ??? flag or counter
246h BYTE line edit (AH=0Ah) insert mode flag (nonzero = on)
247h BYTE canonicalized filename referred to existing file/dir if FFh
248h BYTE ??? flag or counter
249h BYTE type of process termination (00h-03h) (see AH=4Dh)
24Ah BYTE ??? flag
24Bh BYTE value with which to replace first byte of deleted file's name
(normally E5h, but 00h as described under INT 21/AH=13h)
24Ch DWORD pointer to Drive Parameter Block for critical error invocation
250h DWORD pointer to stack frame containing user registers on INT 21
254h WORD stores SP across INT 24
256h DWORD pointer to DOS Drive Parameter Block for ???
25Ah WORD ???
25Ch WORD ??? temp
25Eh WORD ??? flag (only low byte referenced)
260h WORD ??? temp
262h BYTE Media ID byte returned by AH=1Bh,1Ch
263h BYTE ??? (doesn't seem to be referenced)
264h DWORD pointer to device header
268h DWORD pointer to current SFT
26Ch DWORD pointer to current directory structure for drive being accessed
270h DWORD pointer to caller's FCB
274h WORD number of SFT to which file being opened will refer
276h WORD temporary storage for file handle
278h DWORD pointer to a JFT entry in process handle table (see AH=26h)
27Ch WORD offset in DOS DS of first filename argument
27Eh WORD offset in DOS DS of second filename argument
280h WORD offset of last component in pathname or FFFFh
282h WORD ??? offset of transfer address???
284h WORD ??? relative cluster within file being accessed ???
286h WORD ??? absolute cluster number being accessed ???
288h WORD ??? current sector number
28Ah WORD ??? current cluster number
28Ch WORD ??? current offset in file DIV bytes per sector
28Eh 2 BYTEs ???
290h WORD ??? current offset in file MOD bytes per sector
292h DWORD current offset in file
296h WORD ???
298h WORD ???
29Ah WORD ???
29Ch WORD ???
29Eh WORD ???
2A0h WORD ???
2A2h DWORD number of bytes appended to file
2A6h DWORD pointer to ??? disk buffer
2AAh DWORD pointer to working SFT
2AEh WORD used by INT 21 dispatcher to store caller's BX
2B0h WORD used by INT 21 dispatcher to store caller's DS
2B2h WORD temporary storage while saving/restoring caller's registers
2B4h DWORD pointer to prev call frame (offset 250h) if INT 21 reentered
also switched to for duration of INT 24
2B8h 21 BYTEs FindFirst search data for source file(s) of a rename operation
(see AH=4Eh)
2CDh 32 BYTEs directory entry for file being renamed
2EDh 331 BYTEs critical error stack
403h 35 BYTEs scratch SFT
438h 384 BYTEs disk stack (functions greater than 0Ch, INT 25,INT 26)
5B8h 384 BYTEs character I/O stack (functions 01h through 0Ch)
---DOS 3.2,3.3 only---
738h BYTE device driver lookahead flag (see AH=64h)
739h BYTE ??? looks like a drive number
73Ah BYTE ??? flag of some kind
73Ah BYTE ???
----------215D07-----------------------------
INT 21 U - DOS 3.1+ network - GET REDIRECTED PRINTER MODE
AX = 5D07h
Return: DL = mode
00h redirected output is combined
01h redirected output in separate print jobs
SeeAlso: AX=5D08h,AX=5D09h,INT 2F/AX=1125h
----------215D08-----------------------------
INT 21 U - DOS 3.1+ network - SET REDIRECTED PRINTER MODE
AX = 5D08h
DL = mode
00h redirected output is combined
01h redirected output placed in separate jobs, start new print job
now
SeeAlso: AX=5D07h,AX=5D09h,INT 2F/AX=1125h
----------215D09-----------------------------
INT 21 U - DOS 3.1+ network - FLUSH REDIRECTED PRINTER OUTPUT
AX = 5D09h
Note: forces redirected printer output to be printed, and starts a new print
job
SeeAlso: AX=5D07h,AX=5D08h,INT 2F/AX=1125h
----------215D0A-----------------------------
INT 21 - DOS 3.1+ - SET EXTENDED ERROR INFORMATION
AX = 5D0Ah
DS:DX -> 11-word DOS parameter list (see AX=5D00h)
Return: nothing. next call to AH=59h will return values from fields AX,BX,CX,
DX,DI, and ES in corresponding registers
Note: documented for DOS 5+, but undocumented in earlier versions
SeeAlso: AH=59h
----------215D0B-----------------------------
INT 21 U - DOS 4.x only internal - GET DOS SWAPPABLE DATA AREAS
AX = 5D0Bh
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
DS:SI -> swappable data area list (see below)
Note: copying and restoring the swappable data areas allows DOS to be
reentered unless it is in a critical section delimited by calls to
INT 2A/AH=80h and INT 2A/AH=81h,82h
SeeAlso: AX=5D06h,INT 2A/AH=80h,INT 2A/AH=81h,INT 2A/AH=82h
Format of DOS 4.x swappable data area list:
Offset Size Description
00h WORD count of data areas
02h N BYTEs "count" copies of data area record
Offset Size Description
00h DWORD address
04h WORD length and type
bit 15 set if swap always, clear if swap in DOS
bits 14-0: length in bytes
Format of DOS 4.0-5.0 swappable data area:
Offset Size Description
00h BYTE critical error flag
01h BYTE InDOS flag (count of active INT 21 calls)
02h BYTE drive on which current critical error occurred or FFh
03h BYTE locus of last error
04h WORD extended error code of last error
06h BYTE suggested action for last error
07h BYTE class of last error
08h DWORD ES:DI pointer for last error
0Ch DWORD current DTA
10h WORD current PSP
12h WORD stores SP across an INT 23
14h WORD return code from last process termination (zerod after reading
with AH=4Dh)
16h BYTE current drive
17h BYTE extended break flag
18h 2 BYTEs ???
---remainder need only be swapped if in DOS---
1Ah WORD value of AX on call to INT 21
1Ch WORD PSP segment for sharing/network
1Eh WORD network machine number for sharing/network (0000h = us)
20h WORD first usable memory block found when allocating memory
22h WORD best usable memory block found when allocating memory
24h WORD last usable memory block found when allocating memory
26h WORD memory size in paragraphs (used only during initialization)
28h WORD ???
2Ah BYTE ???
2Bh BYTE ???
2Ch BYTE ???
2Dh BYTE ???
2Eh BYTE ???
2Fh BYTE ??? (doesn't seem to be referenced)
30h BYTE day of month
31h BYTE month
32h WORD year - 1980
34h WORD number of days since 1-1-1980
36h BYTE day of week (0 = Sunday)
37h BYTE ???
38h BYTE ???
39h BYTE ???
3Ah 30 BYTEs device driver request header (see INT 2F/AX=0802h)
58h DWORD pointer to device driver entry point (used in calling driver)
5Ch 22 BYTEs device driver request header
72h 30 BYTEs device driver request header
90h 6 BYTEs ???
96h 6 BYTEs CLOCK$ transfer record (see AH=52h)
9Ch 2 BYTEs ???
9Eh 128 BYTEs buffer for filename
11Eh 128 BYTEs buffer for filename
19Eh 21 BYTEs findfirst/findnext search data block (see AH=4Eh)
1B3h 32 BYTEs directory entry for found file
1D3h 88 BYTEs copy of current directory structure for drive being accessed
22Bh 11 BYTEs FCB-format filename for device name comparison
236h BYTE ???
237h 11 BYTEs wildcard destination specification for rename (FCB format)
242h 2 BYTEs ???
244h WORD ???
246h 5 BYTEs ???
24Bh BYTE extended FCB file attributes
24Ch BYTE type of FCB (00h regular, FFh extended)
24Dh BYTE directory search attributes
24Eh BYTE file open mode
24Fh BYTE ??? flag bits
250h BYTE ??? flag or counter
251h BYTE ??? flag
252h BYTE flag indicating how DOS function was invoked
(00h = direct INT 20/INT 21, FFh = server call AX=5D00h)
253h BYTE ???
254h BYTE ???
255h BYTE ???
256h BYTE ???
257h BYTE ???
258h BYTE ???
259h BYTE ???
25Ah BYTE canonicalized filename referred to existing file/dir if FFh
25Bh BYTE ???
25Ch BYTE type of process termination (00h-03h)
25Dh BYTE ???
25Eh BYTE ???
25Fh BYTE ???
260h DWORD pointer to Drive Parameter Block for critical error invocation
264h DWORD pointer to stack frame containing user registers on INT 21
268h WORD stores SP???
26Ah DWORD pointer to DOS Drive Parameter Block for ???
26Eh WORD segment of disk buffer
270h WORD ???
272h WORD ???
274h WORD ???
276h WORD ???
278h BYTE Media ID byte returned by AH=1Bh,1Ch
279h BYTE ??? (doesn't seem to be referenced)
27Ah DWORD pointer to ???
27Eh DWORD pointer to current SFT
282h DWORD pointer to current directory structure for drive being accessed
286h DWORD pointer to caller's FCB
28Ah WORD SFT index to which file being opened will refer
28Ch WORD temporary storage for file handle
28Eh DWORD pointer to a JFT entry in process handle table (see AH=26h)
292h WORD offset in DOS DS of first filename argument
294h WORD offset in DOS DS of second filename argument
296h WORD ???
298h WORD ???
29Ah WORD ???
29Ch WORD ???
29Eh WORD ???
2A0h WORD ???
2A2h WORD ??? directory cluster number???
2A4h DWORD ???
2A8h DWORD ???
2ACh WORD ???
2AEh DWORD offset in file???
2B2h WORD ???
2B4h WORD bytes in partial sector
2B6h WORD number of sectors
2B8h WORD ???
2BAh WORD ???
2BCh WORD ???
2BEh DWORD number of bytes appended to file
2C2h DWORD pointer to ??? disk buffer
2C6h DWORD pointer to ??? SFT
2CAh WORD used by INT 21 dispatcher to store caller's BX
2CCh WORD used by INT 21 dispatcher to store caller's DS
2CEh WORD temporary storage while saving/restoring caller's registers
2D0h DWORD pointer to prev call frame (offset 264h) if INT 21 reentered
also switched to for duration of INT 24
2D4h WORD open mode/action for INT 21/AX=6C00h
2D6h BYTE ??? (set to 00h by INT 21h dispatcher, 02h when a read is
performed, and 01h or 03h by INT 21/AX=6C00h)
2D7h WORD ??? apparently unused
2D9h DWORD stored ES:DI for AX=6C00h
2DDh WORD extended file open action code (see AX=6C00h)
2DFh WORD extended file open attributes (see AX=6C00h)
2E1h WORD extended file open file mode (see AX=6C00h)
2E3h DWORD pointer to filename to open (see AX=6C00h)
2E7h WORD ???
2E9h WORD ???
2EBh BYTE ???
2ECh WORD stores DS during call to [List-of-Lists + 37h]
2EEh WORD ???
2F0h BYTE ???
2F1h WORD ??? bit flags
2F3h DWORD pointer to user-supplied filename
2F7h DWORD pointer to ???
2FBh WORD stores SS during call to [List-of-Lists + 37h]
2FDh WORD stores SP during call to [List-of-Lists + 37h]
2FFh BYTE flag, nonzero if stack switched in calling [List-of-Lists+37h]
300h 21 BYTEs FindFirst search data for source file(s) of a rename operation
(see AH=4Eh)
315h 32 BYTEs directory entry for file being renamed
335h 331 BYTEs critical error stack
480h 384 BYTEs disk stack (functions greater than 0Ch, INT 25,INT 26)
600h 384 BYTEs character I/O stack (functions 01h through 0Ch)
780h BYTE device driver lookahead flag (see AH=64h)
781h BYTE ??? looks like a drive number
782h BYTE ??? flag of some kind
783h BYTE ???
784h WORD ???
786h WORD ???
788h WORD ???
78Ah WORD ???
----------215E00-----------------------------
INT 21 - DOS 3.1+ network - GET MACHINE NAME
AX = 5E00h
DS:DX -> 16-byte buffer for ASCIZ machine name
Return: CF clear if successful
CH = validity
00h name invalid
nonzero valid
CL = NetBIOS number for machine name
DS:DX buffer filled with blank-paded name
CF set on error
AX = error code (01h) (see AH=59h)
Note: supported by OS/2 v1.3+ compatibility box, PC-NFS
SeeAlso: AX=5E01h
----------215E01CH00-------------------------
INT 21 - DOS 3.1+ network - SET MACHINE NAME
AX = 5E01h
CH = 00h undefine name (make it invalid)
<> 0 define name
CL = name number
DS:DX -> 15-character blank-padded ASCIZ name
SeeAlso: AX=5E00h
----------215E02-----------------------------
INT 21 - DOS 3.1+ network - SET NETWORK PRINTER SETUP STRING
AX = 5E02h
BX = redirection list index (see AX=5F02h)
CX = length of setup string
DS:SI -> setup string
Return: CF clear if successful
CF set on error
AX = error code (01h) (see AH=59h)
SeeAlso: AX=5E03h,INT 2F/AX=111Fh
----------215E03-----------------------------
INT 21 - DOS 3.1+ network - GET NETWORK PRINTER SETUP STRING
AX = 5E03h
BX = redirection list index (see AX=5F02h)
ES:DI -> 64-byte buffer for setup string
Return: CF clear if successful
CX = length of setup string
ES:DI buffer filled
CF set on error
AX = error code (01h) (see AH=59h)
SeeAlso: AX=5E02h,INT 2F/AX=111Fh
----------215E04-----------------------------
INT 21 - DOS 3.1+ network - SET PRINTER MODE
AX = 5E04h
BX = redirection list index (see AX=5F02h)
DX = mode
bit 0: set if binary, clear if text (tabs expanded to blanks)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: calls INT 2F/AX=111Fh with 5E04h on stack
SeeAlso: AX=5E05h,INT 2F/AX=111Fh
----------215E05-----------------------------
INT 21 - DOS 3.1+ network - GET PRINTER MODE
AX = 5E05h
BX = redirection list index (see AX=5F02h)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
DX = printer mode (see AX=5E04h)
Note: calls INT 2F/AX=111Fh with 5E05h on stack
SeeAlso: AX=5E04h,INT 2F/AX=111Fh
----------215F00-----------------------------
INT 21 - DOS 3.1+ network - GET REDIRECTION MODE
AX = 5F00h
BL = redirection type
03h printer
04h disk drive
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
BH = redirection state
00h off
01h on
Note: calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F01h,INT 2F/AX=111Eh
----------215F01-----------------------------
INT 21 - DOS 3.1+ network - SET REDIRECTION MODE
AX = 5F01h
BL = redirection type
03h printer
04h disk drive
BH = redirection state
00h off
01h on
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Notes: when redirection is off, the local device (if any) rather than the
remote device is used
calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F00h,INT 2F/AX=111Eh
----------215F02-----------------------------
INT 21 - DOS 3.1+ network, Banyan VINES, PC-NFS - GET REDIRECTION LIST ENTRY
AX = 5F02h
BX = redirection list index
CX = 0000h (LANtastic)
DS:SI -> 16-byte buffer for ASCIZ device name
ES:DI -> 128-byte buffer for ASCIZ network name
Return: CF clear if successful
BH = device status
00h valid
01h invalid
BL = device type
03h printer
04h disk drive
CX = user data previously set with AX=5F03h
DS:SI and ES:DI buffers filled
DX,BP destroyed
CF set on error
AX = error code (01h,12h) (see AH=59h)
Notes: this function is passed through to INT 2F/AX=111Eh
error code 12h is returned if BX is greater than the size of the list
also supported by Banyan VINES, PC-NFS, and LANtastic
SeeAlso: AX=5F03h,INT 2F/AX=111Eh
----------215F03-----------------------------
INT 21 - DOS 3.1+ network, Banyan VINES, LANtastic - REDIRECT DEVICE
AX = 5F03h
BL = device type
03h printer
04h disk drive
CX = user data to save
0000h for LANtastic
DS:SI -> ASCIZ local device name (16 bytes max)
ES:DI -> ASCIZ network name + ASCIZ password (128 bytes max total)
Return: CF clear if successful
CF set on error
AX = error code (01h,03h,05h,08h,0Fh,12h) (see AH=59h)
Notes: if device type is disk drive, DS:SI must point at either a null string
or a string consisting the drive letter followed by a colon; if a
null string, the network attempts to access the destination without
redirecting a local drive
calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F02h,AX=5F04h,INT 2F/AX=111Eh
----------215F04-----------------------------
INT 21 - DOS 3.1+ network, Banyan VINES, LANtastic - CANCEL REDIRECTION
AX = 5F04h
DS:SI -> ASCIZ device name or path
Return: CF clear if successful
CF set on error
AX = error code (01h,03h,05h,08h,0Fh,12h) (see AH=59h)
Notes: the DS:SI string must be either a local device name, a drive letter
followed by a colon, or a network directory beginning with two
backslashes
calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F03h,INT 2F/AX=111Eh
----------215F05-----------------------------
INT 21 - DOS 4.x + Microsoft Networks - GET REDIRECTION LIST EXTENDED ENTRY
AX = 5F05h
BX = redirection list index
DS:SI -> buffer for ASCIZ source device name
ES:DI -> buffer for destination ASCIZ network path
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
BH = device status flag (bit 0 clear if valid)
BL = device type (03h if printer, 04h if drive)
CX = stored parameter value (user data)
BP = NETBIOS local session number
DS:SI buffer filled
ES:DI buffer filled
Notes: the local session number allows sharing the redirector's session number
if an error is caused on the NETBIOS LSN, the redirector may be unable
to correctly recover from errors
calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F06h"Network",INT 2F/AX=111Eh
----------215F05-----------------------------
INT 21 - STARLITE architecture - MAP LOCAL DRIVE LETTER TO REMOTE FILE SYSTEM
AX = 5F05h
DL = drive number (0=A:)
DS:SI -> ASCIZ name of the object to map the drive to
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
SeeAlso: AX=5F06h"STARLITE"
----------215F06-----------------------------
INT 21 U - Network - GET REDIRECTION LIST???
AX = 5F06h
???
Return: ???
Notes: appears to be similar to AX=5F02h and AX=5F05h
calls INT 2F/AX=111Eh with AX on top of the stack
SeeAlso: AX=5F05h"DOS",INT 2F/AX=111Eh
----------215F06-----------------------------
INT 21 - STARLITE architecture - UNMAP DRIVE LETTER
AX = 5F06h
DL = drive to be unmapped (0=A:)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
SeeAlso: AX=5F05h"STARLITE"
----------215F07-----------------------------
INT 21 - DOS 5.0 - ENABLE DRIVE
AX = 5F07h
DL = drive number (0=A:)
Return: CF clear if successful
CF set on error
AX = error code (0Fh) (see AH=59h)
Note: simply sets the "valid" bit in the drive's CDS
SeeAlso: AH=52h,AX=5F08h"DOS"
----------215F07-----------------------------
INT 21 - STARLITE architecture - MAKE NAMED OBJECT AVAILABLE ON NETWORK
AX = 5F07h
DS:SI -> ASCIZ name of object to offer to network
ES:DI -> ASCIZ name under which object will be known on the network
MUST begin with three slashes
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
SeeAlso: AX=5F08h"STARLITE"
----------215F08-----------------------------
INT 21 - DOS 5.0 - DISABLE DRIVE
AX = 5F08h
DL = drive number (0=A:)
Return: CF clear if successful
CF set on error
AX = error code (0Fh) (see AH=59h)
Note: simply clears the "valid" bit in the drive's CDS
SeeAlso: AH=52h,AX=5F07h"DOS"
----------215F08-----------------------------
INT 21 - STARLITE architecture - REMOVE GLOBAL NETWORK NAME OF OBJECT
AX = 5F08h
DS:SI -> ASCIZ network name (not local name) of object to unshare
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
SeeAlso: AX=5F07h"STARLITE"
----------215F09-----------------------------
INT 21 - STARLITE architecture - BIND TO NETWORK DEVICE
AX = 5F09h
DS:DX -> ASCIZ name of the device driver to attach to
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: the STARLITE distributed file system can attach to multiple networks
simultaneously
SeeAlso: AX=5F0Ah
----------215F0A-----------------------------
INT 21 - STARLITE architecture - DETACH FROM NETWORK DEVICE
AX = 5F0Ah
DS:DX -> ASCIZ name of device driver to detach from
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
SeeAlso: AX=5F09h
----------215F32-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosQNmPipeInfo
AX = 5F32h
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F33h,AX=5F34h
----------215F33-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosQNmPHandState
AX = 5F33h
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F32h,AX=5F34h
----------215F34-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosSetNmPHandState
AX = 5F34h
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F32h,AX=5F33h,AX=5F36h
----------215F35-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosPeekNmPipe
AX = 5F35h
???
Note: supported by Novell DOS Named Pipe Extender
Return: ???
SeeAlso: AX=5F38h,AX=5F39h,AX=5F51h
----------215F36-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosTransactNmPipe
AX = 5F36h
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F34h,AX=5F37h
----------215F37-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosCallNmPipe
AX = 5F37h
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F36h,AX=5F38h
----------215F38-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosWaitNmPipe
AX = 5F38h
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F37h,AX=5F39h
----------215F39-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosRawReadNmPipe
AX = 5F39h
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F35h,AX=5F3Ah,INT 2F/AX=1186h
----------215F3A-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosRawWriteNmPipe
AX = 5F3Ah
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F3Bh,INT 2F/AX=118Fh
----------215F3B-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetHandleSetInfo
AX = 5F3Bh
???
Return: ???
SeeAlso: AX=5F3Ch
----------215F3C-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetHandleGetInfo
AX = 5F3Ch
???
Return: ???
SeeAlso: AX=5F3Bh
----------215F40-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetMessageBufferSend
AX = 5F40h
???
Return: ???
----------215F42-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetServiceControl
AX = 5F42h
???
Return: ???
----------215F44-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetWkstaGetInfo
AX = 5F44h
???
Return: ???
SeeAlso: AX=5F45h,AX=5F49h
----------215F45-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetWkstaSetInfo
AX = 5F45h
???
Return: ???
SeeAlso: AX=5F44h
----------215F46-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetUseEnum
AX = 5F46h
???
Return: ???
SeeAlso: AX=5F47h,AX=5F48h,AX=5F4Ch
----------215F47-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetUseAdd
AX = 5F47h
???
Return: ???
SeeAlso: AX=5F46h,AX=5F48h
----------215F48-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetUseDel
AX = 5F48h
???
Return: ???
SeeAlso: AX=5F46h,AX=5F48h,AX=5F49h
----------215F49-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetUseGetInfo
AX = 5F49h
???
Return: ???
SeeAlso: AX=5F44h,AX=5F47h
----------215F4A-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetRemoteCopy
AX = 5F4Ah
???
Return: ???
SeeAlso: AX=5F4Bh
----------215F4B-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetRemoteMove
AX = 5F4Bh
???
Return: ???
SeeAlso: AX=5F4Ah
----------215F4C-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetServerEnum
AX = 5F4Ch
???
Return: ???
Note: supported by Novell DOS Named Pipe Extender
SeeAlso: AX=5F53h
----------215F4D-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosMakeMailslot
AX = 5F4Dh
???
Return: ???
SeeAlso: AX=5F4Eh,AX=5F4Fh,AX=5F50h,AX=5F51h
----------215F4E-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosDeleteMailslot
AX = 5F4Eh
???
Return: ???
SeeAlso: AX=5F4Dh,AX=5F4Fh
----------215F4F-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosMailslotInfo
AX = 5F4Fh
???
Return: ???
SeeAlso: AX=5F4Dh,AX=5F4Eh,AX=5F50h
----------215F50-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosReadMailslot
AX = 5F50h
???
Return: ???
SeeAlso: AX=5F4Dh,AX=5F4Fh,AX=5F51h,AX=5F52h
----------215F51-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosPeekMailslot
AX = 5F51h
???
Return: ???
SeeAlso: AX=5F35h,AX=5F4Fh,AX=5F50h,AX=5F52h
----------215F52-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - DosWriteMailslot
AX = 5F52h
???
Return: ???
SeeAlso: AX=5F4Fh,AX=5F50h,AX=5F51h
----------215F53-----------------------------
INT 21 - LAN Manager Enhanced DOS API local interface - NetServerEnum2
AX = 5F53h
???
Return: ???
SeeAlso: AX=5F4Ch
----------215F80-----------------------------
INT 21 - LANtastic - GET LOGIN ENTRY
AX = 5F80h
BX = login entry index (0-based)
ES:DI -> 16-byte buffer for machine name
Return: CF clear if successful
buffer filled with machine name ("\\" prefix removed)
DL = adapter number (v3+)
CF set on error
AX = error code
Note: the login entry index corresponds to the value BX used in AX=5F83h
SeeAlso: AX=5F83h
----------215F81-----------------------------
INT 21 - LANtastic - LOGIN TO SERVER
AX = 5F81h
ES:DI -> ASCIZ login path followed immediately by ASCIZ password
BL = adapter number
FFh try all valid adapters
00h-07h try only specified adapter
Return: CF clear if successful
CF set on error
AX = error code
Notes: login path is of form "\\machine\username"
if no password is used, the string at ES:DI must be terminated with
three NULs for compatibility with LANtastic v3.0.
SeeAlso: AX=5F82h,AX=5F84h
----------215F82-----------------------------
INT 21 - LANtastic - LOGOUT FROM SERVER
AX = 5F82h
ES:DI -> ASCIZ server name (in form "\\machine")
Return: CF clear if successful
CF set on error
AX = error code
SeeAlso: AX=5F81h,AX=5F88h,AX=5FCBh
----------215F83-----------------------------
INT 21 - LANtastic - GET USERNAME ENTRY
AX = 5F83h
BX = login entry index (0-based)
ES:DI -> 16-byte buffer for username currently logged into
Return: CF clear if successful
DL = adapter number (v3+)
CF set on error
AX = error code
Note: the login entry index corresponds to the value BX used in AX=5F80h
SeeAlso: AX=5F80h
----------215F84-----------------------------
INT 21 - LANtastic - GET INACTIVE SERVER ENTRY
AX = 5F84h
BX = server index not currently logged into
ES:DI -> 16-byte buffer for server name which is available for logging
in to ("\\" prefix omitted)
Return: CF clear if successful
DL = adapter number to non-logged in server is on
CF set on error
AX = error code
SeeAlso: AX=5F81h
----------215F85-----------------------------
INT 21 - LANtastic - CHANGE PASSWORD
AX = 5F85h
ES:DI -> buffer containing "\\machine\oldpassword" 00h "newpassword"00h
Return: CF clear if successful
CF set on error
AX = error code
Notes: must be logged into the named machine
this function is illegal for group accounts
----------215F86-----------------------------
INT 21 - LANtastic - DISABLE ACCOUNT
AX = 5F86h
ES:DI -> ASCIZ machine name and password in form "\\machine\password"
Return: CF clear if successful
CF set on error
AX = error code
Note: must be logged into the named machine and concurrent logins set to 1
by NET_MGR. Requires system manager to re-enable account.
----------215F87-----------------------------
INT 21 - LANtastic v3+ - GET ACCOUNT
AX = 5F87h
DS:SI -> 128-byte buffer for account information (see below)
ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
BX destroyed
Note: must be logged into the specified machine
Format of user account structure:
Offset Size Description
00h 16 BYTEs blank-padded username (zero-padded for v4.x)
10h 16 BYTEs reserved (00h)
20h 32 BYTEs user description
40h BYTE privilege bits
bit 7: bypass access control lists
6: bypass queue protection
5: treat as local process
4: bypass mail protection
3: allow audit entry creation
2: system manager
0: user cannot change password
41h BYTE maximum concurrent users
42h 42 BYTEs bit map for disallowed half hours, beginning on Sunday
(bit set if half-hour not an allowed time)
6Ch WORD internal (0002h)
6Eh 2 WORDs last login time
72h 2 WORDs account expiration date (MSDOS-format year/month:day)
76h 2 WORDs password expiration date (0 = none)
7Ah BYTE number of days to extend password after change (1-31)
00h if no extension required
---v3.x---
7Bh 5 BYTEs reserved
---v4.x---
7Bh BYTE storage for first letter of user name when deleted (first
character is changed to 00h when deleting account)
7Ch BYTE extended privileges
7Dh 3 BYTEs reserved
----------215F88-----------------------------
INT 21 - LANtastic v4.0+ - LOGOUT FROM ALL SERVERS
AX = 5F88h
Return: CF clear if successful
CF set on error
AX = error code
SeeAlso: AX=5F82h
----------215F97-----------------------------
INT 21 - LANtastic - COPY FILE
AX = 5F97h
CX:DX = number of bytes to copy (FFFFFFFFh = entire file)
SI = source file handle
DI = destination file handle
Return: CF clear if successful
DX:AX = number of bytes copied
CF set on error
AX = error code
Note: copy is performed by server
----------215F98-----------------------------
INT 21 - LANtastic - SEND UNSOLICITED MESSAGE
AX = 5F98h
DS:SI -> message buffer (see below)
Return: CF clear if successful
CF set on error
AX = error code
Note: v4.1- return no errors
SeeAlso: AX=5F99h
Format of message buffer:
Offset Size Description
00h BYTE reserved
01h BYTE message type
00h general
01h server warning
02h-7Fh reserved
80h-FFh user-defined
02h 16 BYTEs ASCIZ destination machine name
12h 16 BYTEs ASCIZ server name which user must be logged into
22h 16 BYTEs ASCIZ user name
32h 16 BYTEs ASCIZ originating machine name (filled in when received)
42h 80 BYTEs message text
----------215F99-----------------------------
INT 21 - LANtastic - GET LAST RECEIVED UNSOLICITED MESSAGE
AX = 5F99h
ES:DI -> messsage buffer (see AX=5F98h for format)
Return: CF clear if successful
CF set on error
AX = error code
SeeAlso: AX=5F98h
----------215F9A-----------------------------
INT 21 - LANtastic - GET MESSAGE PROCESSING FLAGS
AX = 5F9Ah
Return: CF clear if successful
DL = bits describing processing for received unsolicited messages
bit 0: beep before message is delivered
1: deliver message to message service
2: pop up message automatically (v3+)
CF set on error
AX = error code
SeeAlso: AX=5F9Bh,AX=5F9Ch,AX=5F9Dh
----------215F9B-----------------------------
INT 21 - LANtastic - SET MESSAGE PROCESSING FLAG
AX = 5F9Bh
DL = bits describing processing for received unsolicited messages
(see AX=5F9Ah)
Return: CF clear if successful
CF set on error
AX = error code
SeeAlso: AX=5F9Ah,AX=5F9Eh
----------215F9C-----------------------------
INT 21 - LANtastic v3+ - POP UP LAST RECEIVED MESSAGE
AX = 5F9Ch
CX = time to leave on screen in clock ticks
DH = 0-based screen line on which to place message
Return: CF clear if successful
CF set on error
AX = error code (0Bh)
Notes: the original screen contents are restored when the message is removed
the message will not appear, and an error will be returned, if the
screen is in a graphics mode
SeeAlso: AX=5F9Ah
----------215F9D-----------------------------
INT 21 - LANtastic v4.1+ - GET REDIRECTOR CONTROL BITS
AX = 5F9Dh
Return: DL = redirector control bits
bit 7: set to notify on print job completion
SeeAlso: AX=5F9Ah,AX=5F9Eh
----------215F9E-----------------------------
INT 21 - LANtastic v4.1+ - SET REDIRECTOR CONTROL BITS
AX = 5F9Eh
DL = redirector control bits (see AH = 5F9Dh)
Return: nothing
SeeAlso: AX=5F9Bh,AX=5F9Dh
----------215FA0-----------------------------
INT 21 - LANtastic - GET QUEUE ENTRY
AX = 5FA0h
BX = queue entry index (0000h is first entry)
DS:SI -> buffer for queue entry (see below)
ES:DI -> ASCIZ server name in form "\\name"
Return: CF clear if successful
CF set on error
AX = error code
BX = entry index for next queue entry (BX-1 is current index)
SeeAlso: AX=5FA1h,AX=5FA2h
Format of queue entry:
Offset Size Description
00h BYTE status of entry
00h empty
01h being updated
02h being held
03h waiting for despool
04h being despooled
05h canceled
06h spooled file could not be accessed
07h destination could not be accessed
08h rush job
01h DWORD size of spooled file
05h BYTE type of entry
00h printer queue file
01h message
02h local file
03h remote file
04h to remote modem
05h batch processor file
06h BYTE output control
bit 6: don't delete (for mail)
bit 5: mail file contains voice mail (v3+)
bit 4: mail message has been read
bit 3: response has been requested for this mail
07h WORD number of copies
09h DWORD sequence number of queue entry
0Dh 48 BYTEs pathname of spooled file
3Dh 16 BYTEs user who spooled file
4Dh 16 BYTEs name of machine from which file was spooled
5Dh WORD date file was spooled (see AX=5700h)
5Fh WORD time file was spooled (see AX=5700h)
61h 17 BYTEs ASCIZ destination device or user name
72h 48 BYTEs comment field
----------215FA1-----------------------------
INT 21 - LANtastic - SET QUEUE ENTRY
AX = 5FA1h
BX = handle of opened queue entry
DS:SI -> queue entry (see AX=5FA0h)
Return: CF clear if successful
CF set on error
AX = error code
Notes: the only queue entry fields which may be changed are output control,
number of copies, destination device, and comment
the handle in BX is that from a create or open (INT 21/AH=3Ch,3Dh)
call on the file "\\server\\@MAIL" or "\\server\@name" (for
printer queue entries)
SeeAlso: AX=5FA0h,AX=5FA2h,AX=5FA9h
----------215FA2-----------------------------
INT 21 - LANtastic - CONTROL QUEUE
AX = 5FA2h
BL = control command
00h start despooling (privileged)
01h halt despooling (privileged)
02h halt despooling at end of job (privileged)
03h pause despooler at end of job (privileged)
04h print single job (privileged)
05h restart current job (privileged)
06h cancel the current job
07h hold queue entry
08h release a held queue entry
09h make queue entry a rushed job (privileged)
CX:DX = sequence number to control (commands 06h-09h)
DX = physical printer number (commands 00h-05h)
00h-02h LPT1-LPT3
03h,04h COM1,COM2
other all printers
ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
----------215FA3-----------------------------
INT 21 - LANtastic v3+ - GET PRINTER STATUS
AX = 5FA3h
BX = physical printer number (00h-02h = LPT1-LPT3, 03h-04h = COM1-COM2)
DS:SI -> buffer for printer status (see below)
ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
BX = next physical printer number
Note: you must be logged in to the specified server
Format of printer status:
Offset Size Description
00h BYTE printer state
bit 7: printer paused
bits 0-6: 0 printer disabled
1 will stop at end of job
2 print multiple jobs
01h WORD queue index of print job being despooled
FFFFh if not despooling--ignore all following fields
03h WORD actual characters per second being output
05h DWORD number of characters actually output so far
09h DWORD number of bytes read from spooled file so far
0Dh WORD copies remaining to print
----------215FA4-----------------------------
INT 21 - LANtastic v3+ - GET STREAM INFO
AX = 5FA4h
BX = 0-based stream index number
DS:SI -> buffer for stream information (see below)
ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
BX = next stream number
SeeAlso: AX=5FA5h
Format of stream information:
Offset Size Description
00h BYTE queueing of jobs for logical printer (0=disabled,other=enabled)
01h 11 BYTEs logical printer resource template (may contain ? wildcards)
----------215FA5-----------------------------
INT 21 - LANtastic v3+ - SET STREAM INFO
AX = 5FA5h
BX = 0-based stream index number
DS:SI -> buffer containing stream information (see AX=5FA4h)
ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
SeeAlso: AX=5FA4h
----------215FA7-----------------------------
INT 21 - LANtastic - CREATE USER AUDIT ENTRY
AX = 5FA7h
DS:DX -> ASCIZ reason code (max 8 bytes)
DS:SI -> ASCIZ variable reason string (max 128 bytes)
ES:DI -> ASCIZ machine name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
Note: you must be logged in to the specified server and have the "U"
privilege to execute this call
----------215FA9-----------------------------
INT 21 - LANtastic v4.1+ - SET EXTENDED QUEUE ENTRY
AX = 5FA9h
BX = handle of opened queue entry
DS:SI -> queue entry (see AX=5FA0h)
Return: CF clear if successful
CF set on error
AX = error code
Note: functions exactly the same as AX=5FA1h except the spooled filename is
also set. This call supports direct despooling.
SeeAlso: AX=5FA1h
----------215FB0-----------------------------
INT 21 - LANtastic - GET ACTIVE USER INFORMATION
AX = 5FB0h
BX = server login entry index
DS:SI -> buffer for active user entry (see below)
ES:DI -> ASCIZ machine name in form "\\server"
Return: CF clear if successful
CF set on error
AX = error code
BX = next login index
Format of active user entry:
Offset Size Description
00h WORD virtual circuit number
02h BYTE login state
bit 0: fully logged in
1: remote program load login
2: user has system manager privileges
3: user can create audit entries
4: bypass mail protection
5: treat as local process
6: bypass queue protection
7: bypass access control lists
03h BYTE last command issued (see below)
04h 5 BYTEs number of I/O bytes (40-bit unsigned number)
09h 3 BYTEs number of server requests (24-bit unsigned)
0Ch 16 BYTEs name of user who is logged in
1Ch 16 BYTEs name of remote logged in machine
2Ch BYTE extended privileges (v4+???)
bit 0: user cannot change his password
2Dh WORD time left in minutes (0000h = unlimited) (v4+???)
Values for last command:
00h login
01h process termination
02h open file
03h close file
04h create file
05h create new file
06h create unique file
07h commit data to disk
08h read file
09h write file
0Ah delete file
0Bh set file attributes
0Ch lock byte range
0Dh unlock byte range
0Eh create subdirectory
0Fh remove subdirectory
10h rename file
11h find first matching file
12h find next matching file
13h get disk free space
14h get a queue entry
15h set a queue entry
16h control the queue
17h return login information
18h return link description
19h seek on file
1Ah get server's time
1Bh create audit entry
1Ch open file in multitude of modes
1Dh change password
1Eh disable account
1Fh local server file copy
---v3+---
20h get username from account file
21h translate server's logical path
22h make indirect file
23h get indirect file contents
24h get physical printer status
25h get logical print stream info
26h set logical print stream info
27h get user's account record
---v4+---
28h request server shutdown
29h cancel server shutdown
2Ah stuff server's keyboard
2Bh write then commit data to disk
2Ch set extended queue entry
2Dh terminate user from server
2Eh enable/disable logins
2Fh flush server caches
30h change username
31h get extended queue entry
(same as get queue, but can return named fields blanked)
----------215FB1-----------------------------
INT 21 - LANtastic - GET SHARED DIRECTORY INFORMATION
AX = 5FB1h
DS:SI -> 64-byte buffer for link description
ES:DI -> ASCIZ machine and shared directory name in form
"\\machine\shared-resource"
Return: CF clear if successful
CX = access control list privilege bits for requesting user
bit 4: (I) allow expansion of indirect files
5: (A) allow attribute changing
6: (P) allow physical access to device
7: (E) allow program execution
8: (N) allow file renaming
9: (K) allow directory deletion
10: (D) allow file deletion
11: (L) allow file/directory lookups
12: (M) allow directory creation
13: (C) allow file creation
14: (W) allow open for write and writing
15: (R) allow open for read and reading
CF set on error
AX = error code
----------215FB2-----------------------------
INT 21 - LANtastic v3+ - GET USERNAME FROM ACCOUNT FILE
AX = 5FB2h
BX = username entry index (0 for first)
DS:SI -> 16-byte buffer for username
ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
BX = next queue entry index
----------215FB3-----------------------------
INT 21 - LANtastic v3+ - TRANSLATE PATH
AX = 5FB3h
DS:SI -> 128-byte buffer for ASCIZ result
ES:DI -> full ASCIZ path, including server name
DX = types of translation to be performed
bit 0: expand last component as indirect file
1: return actual path relative to server's physical disk
Return: CF clear if successful
CF set on error
AX = error code
Note: always expands any indirect files along the path
SeeALso: AX=5FB4h
----------215FB4-----------------------------
INT 21 - LANtastic v3+ - CREATE INDIRECT FILE
AX = 5FB4h
DS:SI -> 128-byte buffer containing ASCIZ contents of indirect file
ES:DI -> full ASCIZ path of indirect file to create, incl machine name
Return: CF clear if successful
CF set on error
AX = error code
Note: the contents of the indirect file may be any valid server-relative path
----------215FB5-----------------------------
INT 21 - LANtastic v3+ - GET INDIRECT FILE CONTENTS
AX = 5FB5h
DS:SI -> 128-byte buffer for ASCIZ indirect file contents
ES:DI -> full ASCIZ path of indirect file
Return: CF clear if successful
CF set on error
AX = error code
----------215FB6-----------------------------
INT 21 - LANtastic v4.1+ - SET AUTO-LOGIN DEFAULTS
AX = 5FB6h
ES:DI -> pointer to ASCIZ default user name, immediately followed by
ASCIZ password
BL = adapter number to use for default login attempt
FFh try all valid adapters
00h-05h try adapter 0-5 explicitly
Return: CF clear if successful
CF set on error
AX = error code
Notes: call with ES:DI -> two nulls to disable auto-login
SeeAlso: AX=5FB7h
----------215FB7-----------------------------
INT 21 - LANtastic v4.1+ - GET AUTO-LOGIN DEFAULTS
AX = 5FB7h
ES:DI -> pointer to 16-byte buffer to store ASCIZ auto-login user name
Return: CF clear if successful
DL = adapter number used for default login attempt
FFh all valid adapters will be tried
00h-05h specified adapter will be tried explicitly
CF set on error
AX = error code
SeeAlso: AX=5F81h,AX=5FB6h
----------215FC0-----------------------------
INT 21 - LANtastic - GET TIME FROM SERVER
AX = 5FC0h
DS:SI -> time block (see below)
ES:DI -> ASCIZ server name to get time from
Return: CF clear if successful
CF set on error
AX = error code
Format of time block:
Offset Size Description
00h WORD year
02h BYTE day
03h BYTE month
04h BYTE minutes
05h BYTE hour
06h BYTE hundredths of second
07h BYTE second
----------215FC8-----------------------------
INT 21 - LANtastic v4.0+ - SCHEDULE SERVER SHUTDOWN
AX = 5FC8h
ES:DI -> ASCIZ server name in form "\\machine"
DS:SI -> ASCIZ reason string (80 characters)
CX = number of minutes until shutdown (0 = immediate)
DX = option flags (see below)
bit 0: auto reboot
1: do not notify users
2: halt after shutdown
3: shutdown due to power fail (used by UPS)
bits 4-7: reserved
bits 8-14: user definable
bit 15: reserved
Return: CF clear if successful
CF set on error
AX = error code
SeeAlso: AH=5FC9h
----------215FC9-----------------------------
INT 21 - LANtastic v4.0+ - CANCEL SERVER SHUTDOWN
AX = 5FC9h
ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
Note: you must have the "S" privilege to use this call
SeeAlso: AH=5FC8h
----------215FCA-----------------------------
INT 21 - LANtastic v4.0+ - STUFF SERVER KEYBOARD BUFFER
AX = 5FCAh
ES:DI -> ASCIZ server name in form "\\machine"
DS:SI -> ASCIZ string to stuff (128 bytes)
Return: CF clear if successful
CF set on error
AX = error code
Note: you must have the "S" privilege to use this call
maximum number of characters that can be stuffed is determined by the
server's RUN BUFFER SIZE.
----------215FCB-----------------------------
INT 21 - LANtastic v4.1+ - TERMINATE USER
AX = 5FCBh
ES:DI -> ASCIZ server name in form "\\machine"
DS:SI -> blank-padded username. A null char = wildcard.
DS:DX -> blank-padded machine name. A null char = wildcard.
CX = minutes until termination (0 = immediate)
Return: CF clear if successful
CF set on error
AX = error code
Note: you must have the "S" privilege to use this call
you cannot log yourself out using this call
SeeAlso: AX=5F82h
----------215FCC-----------------------------
INT 21 - LANtastic v4.1+ - GET/SET SERVER CONTROL BITS
AX = 5FCCh
ES:DI -> ASCIZ server name in form "\\machine"
CX = bit values (value of bits you want to set) See below.
DX = bit mask (bits you are interested in, 0 = get only) See
below.
Return: CF clear if successful
CX = control bits after call
bit 0: disable logins
CF set on error
AX = error code
Note: you must have the "S" privilege to SET, anyone can GET.
----------215FCD-----------------------------
INT 21 - LANtastic v4.1+ - FLUSH SERVER CACHES
AX = 5FCDh
ES:DI -> ASCIZ server name in form "\\machine"
Return: CF clear if successful
CF set on error
AX = error code
Note: you must have the "S" privilege to use this call.
----------215FD0-----------------------------
INT 21 - LANtastic - GET REDIRECTED PRINTER TIMEOUT
AX = 5FD0h
Return: CF clear if successful
CX = redirected printer timeout in clock ticks of 55ms
0000h if timeout disabled
CF set on error
AX = error code
SeeAlso: AX=5FD1h
----------215FD1-----------------------------
INT 21 - LANtastic - SET REDIRECTED PRINTER TIMEOUT
AX = 5FD1h
CX = printer timeout in clock ticks of 55ms, 0000h to disable timeouts
Return: CF clear if successful
CF set on error
AX = error code
SeeAlso: AX=5FD0h
----------215FE0-----------------------------
INT 21 - LANtastic - GET DOS SERVICE VECTOR
AX = 5FE0h
Return: CF clear if successful
ES:BX -> current FAR service routine
CF set on error
AX = error code
Note: the service routine is called by the LANtastic redirector whenever DOS
may safely be called, permitting external TSRs and drivers to hook
into LANtastic's DOS busy flag checking
SeeAlso: AX=5FE1h,INT 28,INT 2A/AH=84h
----------215FE1-----------------------------
INT 21 - LANtastic - SET DOS SERVICE VECTOR
AX = 5FE1h
ES:BX -> FAR routine to call when DOS services are available
Return: CF clear if successful
CF set on error
AX = error code
Note: new handler must chain to previous handler as its first action
SeeAlso: AX=5FE0h
----------215FE2-----------------------------
INT 21 - LANtastic - GET MESSAGE SERVICE VECTOR
AX = 5FE2h
Return: CF clear if successful
ES:BX -> current FAR message service routine
CF set on error
AX = error code
SeeAlso: AX=5FE3h
----------215FE3-----------------------------
INT 21 - LANtastic - SET MESSAGE SERVICE VECTOR
AX = 5FE3h
ES:BX -> FAR routine for processing network messages
Return: CF clear if successful
CF set on error
AX = error code
Notes: handler must chain to previous handler as its first action
on invocation, ES:BX -> just-received message
SeeAlso: AX=5FE2h
----------2160-------------------------------
INT 21 - DOS 3.0+ - CANONICALIZE FILENAME OR PATH
AH = 60h
DS:SI -> ASCIZ filename or path
ES:DI -> 128-byte buffer for canonicalized name
Return: CF set on error
AX = error code
02h invalid component in directory path or drive letter only
03h malformed path or invalid drive letter
ES:DI buffer unchanged
CF clear if successful
AH = 00h
AL = destroyed (00h or 5Ch or last char of current dir on drive)
buffer filled with qualified name of form D:\PATH\FILE.EXT or
\\MACHINE\PATH\FILE.EXT
Notes: the input path need not actually exist
letters are uppercased, forward slashes converted to backslashes,
asterisks converted to appropriate number of question marks, and
file and directory names are truncated to 8.3 if necessary.
'.' and '..' in the path are resolved
filespecs on local drives always start with "d:", those on network
drives always start with "\\"
if path string is on a JOINed drive, the returned name is the one that
would be needed if the drive were not JOINed; similarly for a
SUBSTed, ASSIGNed, or network drive letter. Because of this, it is
possible to get a qualified name that is not legal under the current
combination of SUBSTs, ASSIGNs, JOINs, and network redirections
under DOS 3.3 through 5.00, a device name is translated differently if
the device name does not have an explicit directory or the directory
is \DEV (relative directory DEV from the root directory works
correctly). In these cases, the returned string consists of the
unchanged device name and extension appended to the string X:/
(forward slash instead of backward slash as in all other cases) where
X is the default or explicit drive letter.
functions which take pathnames require canonical paths if invoked via
INT 21/AX=5D00h
supported by OS/2 v1.1 compatibility box
NetWare 2.1x does not support characters with the high bit set; early
versions of NetWare 386 support such characters except in this call.
In addition, NetWare returns error code 3 for the path "X:\"; one
should use "X:\." instead.
for DOS 3.3-5.0, the input and output buffers may be the same, as the
canonicalized name is built in an internal buffer and copied to the
specified output buffer as the very last step
for DR DOS 6.0, this function is not automatically called when on a
network. Device drivers reportedly cannot make this call from their
INIT function. Using the same pointer for both input and output
buffers is not supported in the April 1992 and earlier versions of
DR DOS
SeeAlso: INT 2F/AX=1123h,INT 2F/AX=1221h
----------2161-------------------------------
INT 21 - DOS 3+ - UNUSED
AH = 61h
Return: AL = 00h
Note: this function does nothing and returns immediately
----------2162-------------------------------
INT 21 - DOS 3+ - GET CURRENT PSP ADDRESS
AH = 62h
Return: BX = segment of PSP for current process
Notes: under DOS 3+, this function does not use any of the DOS-internal stacks
and may thus be called at any time, even during another INT 21h call
the current PSP is not necessarily the caller's PSP
identical to the undocumented AH=51h
SeeAlso: AH=50h,AH=51h
----------216300-----------------------------
INT 21 - DOS 2.25 only - GET LEAD BYTE TABLE ADDRESS
AX = 6300h
Return: CF clear if successful
DS:SI -> lead byte table (see below)
CF set on error
AX = error code (01h) (see AH=59h)
Notes: does not preserve any registers other than SS:SP
the US version of MSDOS 3.30 treats this as an unused function,
setting AL=00h and returning immediately
SeeAlso: AX=6301h,AH=07h,AH=08h,AH=0Bh
Format of lead byte table entry:
Offset Size Description
00h 2 BYTEs low/high ends of a range of leading byte of double-byte chars
02h 2 BYTEs low/high ends of a range of leading byte of double-byte chars
...
N 2 BYTEs 00h,00h end flag
----------216300-----------------------------
INT 21 - Far East DOS 3.2+ - GET DOUBLE BYTE CHARACTER SET LEAD TABLE
AX = 6300h
Return: AL = error code
00h successful
DS:SI -> DBCS table (see below)
all other registers except CS:IP and SS:SP destroyed
FFh not supported
Notes: probably identical to AH=63h/AL=00h for DOS 2.25
the US version of MSDOS 3.30 treats this as an unused function,
setting AL=00h and returning immediately
the US version of DOS 4.0+ accepts this function, but returns an empty
list
SeeAlso: AX=6300h"DOS 2.25"
Format of DBCS table:
Offset Size Description
00h 2 BYTEs low/high ends of a range of leading byte of double-byte chars
02h 2 BYTEs low/high ends of a range of leading byte of double-byte chars
...
N 2 BYTEs 00h,00h end flag
----------216301-----------------------------
INT 21 - DOS 2.25, Far East DOS 3.2+ - SET KOREAN (HANGUL) INPUT MODE
AX = 6301h
DL = new mode
00h return only full characters on DOS keyboard input functions
01h return partially-formed characters also
Return: AL = status
00h successful
FFh invalid mode
SeeAlso: AH=07h,AH=08h,AH=0Bh,AH=63h,AX=6302h
----------216302-----------------------------
INT 21 - DOS 2.25, Far East DOS 3.2+ - GET KOREAN (HANGUL) INPUT MODE
AX = 6302h
Return: AL = status
00h successful
DL = current input mode
00h return only full characters
01h return partial characters
FFh not supported
SeeAlso: AH=07h,AH=08h,AH=0Bh,AH=63h,AX=6301h
----------2164-------------------------------
INT 21 - DOS 3.2+ internal - SET DEVICE DRIVER LOOKAHEAD FLAG
AH = 64h
AL = flag
00h (default) call device driver function 5 (non-dest read)
before INT 21/AH=01h,08h,0Ah
nonzero don't call driver function 5
Return: nothing
Notes: called by DOS 3.3+ PRINT.COM
does not use any of the DOS-internal stacks and is thus fully
reentrant
SeeAlso: AH=01h,AH=08h,AH=0Ah,AX=5D06h
----------2164--BX0000-----------------------
INT 21 - OS/2 v2.0 Virtual DOS Machine - GET/SET TASK TITLE
AH = 64h
BX = 0000h
CX = 636Ch
DX = function
0000h enable automatic title switch on INT 21/AH=4Bh
0001h set session title
ES:DI -> new ASCIZ title or "" to restore original title
0002h get session title
ES:DI -> buffer for current title
Return: buffer filled (single 00h if title never changed)
SeeAlso: INT 15/AH=12h/BH=05h,INT 21/AH=4Bh
----------2165-------------------------------
INT 21 - DOS 3.3+ - GET EXTENDED COUNTRY INFORMATION
AH = 65h
AL = info ID
01h get general internationalization info
02h get pointer to uppercase table
04h get pointer to filename uppercase table
05h get pointer to filename terminator table
06h get pointer to collating sequence table
07h (DOS 4+) get pointer to Double-Byte Character Set table
BX = code page (-1=global code page)
DX = country ID (-1=current country)
ES:DI -> country information buffer (see below)
CX = size of buffer (>= 5)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if succesful
CX = size of country information returned
ES:DI -> country information
Notes: AL=05h appears to return same info for all countries and codepages; it
has been documented for DOS 5.0, but was undocumented in ealier
versions
NLSFUNC must be installed to get info for countries other than the
default
subfunctions 02h and 04h are identical under OS/2
SeeAlso: AH=38h,INT 2F/AX=1401h,INT 2F/AX=1402h
Format of country information:
Offset Size Description
00h BYTE info ID
---if info ID = 01h---
01h WORD size
03h WORD country ID
05h WORD code page
07h 34 BYTEs country-dependent info (see AH=38h)
---if info ID = 02h---
01h DWORD pointer to uppercase table (see below)
---if info ID = 04h---
01h DWORD pointer to filename uppercase table (see below)
---if info ID = 05h---
01h DWORD pointer to filename character table (see below)
---if info ID = 06h---
01h DWORD pointer to collating table (see below)
---if info ID = 07h (DOS 4+)---
01h DWORD pointer to DBCS lead byte table (see below)
Format of uppercase table:
Offset Size Description
00h WORD table size
02h 128 BYTEs uppercase equivalents (if any) of chars 80h to FFh
Format of collating table:
Offset Size Description
00h WORD table size
02h 256 BYTEs values used to sort characters 00h to FFh
Format of filename terminator table:
Offset Size Description
00h WORD table size (not counting this word)
02h BYTE ??? (01h for MSDOS 3.30-5.00)
03h BYTE lowest permissible character value for filename
04h BYTE highest permissible character value for filename
05h BYTE ??? (00h for MSDOS 3.30-5.00)
06h BYTE first excluded character in range \ all characters in this
07h BYTE last excluded character in range / range are illegal
08h BYTE ??? (02h for MSDOS 3.30-5.00)
09h BYTE number of illegal (terminator) characters
0Ah N BYTES characters which terminate a filename: ."/\[]:|<>+=;,
Note: partially documented for DOS 5.0, but undocumented for earlier versions
Format of filename uppercase table:
Offset Size Description
00h WORD table size
02h 128 BYTEs uppercase equivalents (if any) of chars 80h to FFh
Format of DBCS lead byte table:
Offset Size Description
00h WORD length
02h 2N BYTEs start/end for N lead byte ranges
WORD 0000h (end of table)
----------2165-------------------------------
INT 21 - DOS 4+ - COUNTRY-DEPENDENT CHARACTER CAPITALIZATION
AH = 65h
AL = function
20h capitalize character
DL = character to capitalize
Return: DL = capitalized character
21h capitalize string
DS:DX -> string to capitalize
CX = length of string
22h capitalize ASCIZ string
DS:DX -> ASCIZ string to capitalize
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: these calls have been documented for DOS 5+, but were undocumented in
DOS 4.x.
----------216523-----------------------------
INT 21 U - DOS 4+ internal - DETERMINE IF CHARACTER REPRESENTS YES/NO RESPONSE
AX = 6523h
DL = character
DH = second character of double-byte character (if applicable)
Return: CF set on error
CF clear if successful
AX = type
00h no
01h yes
02h neither yes nor no
----------2165-------------------------------
INT 21 U - DOS 4+ internal - COUNTRY-DEPENDENT FILENAME CAPITALIZATION
AH = 65h
AL = function
A0h capitalize filename character
DL = character to capitalize
Return: DL = capitalized character
A1h capitalize counted filename string
DS:DX -> filename string to capitalize
CX = length of string
A2h capitalize ASCIZ filename
DS:DX -> ASCIZ filename to capitalize
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
Note: nonfunctional in DOS 4.00 through 5.00 due to a bug (the code sets a
pointer depending on the high bit of AL, but doesn't clear the
bit before branching by function number).
----------216601-----------------------------
INT 21 - DOS 3.3+ - GET GLOBAL CODE PAGE TABLE
AX = 6601h
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
BX = active code page (see AX=6602h)
DX = system code page
SeeAlso: AX=6602h
----------216602-----------------------------
INT 21 - DOS 3.3+ - SET GLOBAL CODE PAGE TABLE
AX = 6602h
BX = active code page
437 US
850 Multilingual
852 Slavic/Latin II (DOS 5+)
857 Turkish
860 Portugal
861 Iceland
863 Canada (French)
865 Norway/Denmark
DX = system code page (active page at boot time)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
SeeAlso: AX=6601h
----------2167-------------------------------
INT 21 - DOS 3.3+ - SET HANDLE COUNT
AH = 67h
BX = size of new file handle table for process
Return: CF clear if successful
CF set on error
AX = error code (see AH=59h)
Desc: adjust the size of the per-process open file table, thus raising or
lowering the limit on the number of files the caller can open
simultaneously
Notes: if BX <= 20, no action is taken if the handle limit has not yet been
increased, and the table is copied back into the PSP if the limit
is currently > 20 handles
for file handle tables of > 20 handles, DOS 3.30 never reuses the
same memory block, even if the limit is being reduced; this can lead
to memory fragmentation as a new block is allocated and the existing
one freed
only the first 20 handles are copied to child processes in DOS 3.3
BUG: the original release of DOS 3.30 allocates a full 64K for the handle
table on requests for an even number of handles
SeeAlso: AH=26h,AH=86h
----------2168-------------------------------
INT 21 - DOS 3.3+ - "FFLUSH" - COMMIT FILE
AH = 68h
BX = file handle
Return: CF clear if successful
all data still in DOS disk buffers is written to disk immediately,
and the file's directory entry is updated
CF set on error
AX = error code (see AH=59h)
SeeAlso: AX=5D01h,AH=6Ah,INT 2F/AX=1107h
----------2169-------------------------------
INT 21 U - DOS 4+ internal - GET/SET DISK SERIAL NUMBER
AH = 69h
AL = subfunction
00h get serial number
01h set serial number
BL = drive (0=default, 1=A, 2=B, etc)
DS:DX -> disk info (see below)
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
AX destroyed
(AL = 00h) buffer filled with appropriate values from extended BPB
(AL = 01h) extended BPB on disk set to values from buffer
Notes: does not generate a critical error; all errors are returned in AX
error 0005h given if no extended BPB on disk
does not work on network drives (error 0001h)
buffer after first two bytes is exact copy of bytes 27h thru 3Dh of
extended BPB on disk
this function is supported under Novell NetWare versions 2.0A through
3.11; the returned serial number is the one a DIR would display,
the volume label is the NetWare volume label, and the file system
is set to "FAT16".
SeeAlso: AX=440Dh
Format of disk info:
Offset Size Description
00h WORD info level (zero)
02h DWORD disk serial number (binary)
06h 11 BYTEs volume label or "NO NAME " if none present
11h 8 BYTEs (AL=00h only) filesystem type--string "FAT12 " or "FAT16 "
----------2169-------------------------------
INT 21 - DR-DOS 5.0 - NULL FUNCTION
AH = 69h
Return: AL = 00h
SeeAlso: AH=18h
----------216969-----------------------------
INT 21 - VIRUS - "Rape-747" - INSTALLATION CHECK
AX = 6969h
Return: AX = 0666h if resident
SeeAlso: AX=58CCh,AH=76h"VIRUS"
----------216A-------------------------------
INT 21 U - DOS 4+ - COMMIT FILE
AH = 6Ah
BX = file handle
Return: CF clear if successful
AH = 68h
CF set on error
AX = error code (06h) (see AH=59h)
Note: identical to AH=68h in DOS 5.0; not known whether this is the case in
DOS 4.x
SeeAlso: AH=68h
----------216B-------------------------------
INT 21 U - DOS 4.0 internal - ???
AH = 6Bh
AL = subfunction
00h ???
DS:SI -> Current Directory Structure???
CL = drive (1=A:)
01h ???
DS:SI -> ???
CL = file handle???
02h ???
DS:SI -> Current Directory Structure???
DI = ???
CX = drive (1=A:)
Return: CF set on error
AX = error code (see INT 21/AH=59h)
CF clear if successful
Note: passed through to INT 2F/AX=112Fh with AX on top of stack
SeeAlso: AH=6Bh"DOS 5",INT 2F/AX=112Fh
----------216B-------------------------------
INT 21 U - DOS 5.0 - NULL FUNCTION
AH = 6Bh
Return: AL = 00h
Note: this function does nothing and returns immediately
SeeAlso: AH=6Bh"DOS 4"
----------216C00-----------------------------
INT 21 - DOS 4+ - EXTENDED OPEN/CREATE
AX = 6C00h
BL = open mode as in AL for normal open (INT 21/AH=3Dh)
bit 7: inheritance
bits 4-6: sharing mode
bit 3 reserved
bits 0-2: access mode
BH = flags
bit 6 = auto commit on every write
bit 5 = return error rather than doing INT 24h
CX = create attribute
bits 6-15 reserved
bit 5: archive
bit 4: reserved
bit 3: volume label
bit 2: system
bit 1: hidden
bit 0: readonly
DL = action if file exists/does not exists
bits 7-4 action if file does not exist
0000 fail
0001 create
bits 3-0 action if file exists
0000 fail
0001 open
0010 replace/open
DH = 00h (reserved)
DS:SI -> ASCIZ file name
Return: CF set on error
AX = error code (see AH=59h)
CF clear if successful
AX = file handle
CX = 1 file opened
2 file created
3 file replaced
Note: the PC LAN Program only supports DL=01h, DL=10h/sharing=compatibility,
and DL=12h
SeeAlso: AH=3Ch,AH=3Dh
----------217070BX6060-----------------------
INT 21 - PCW Weather Card interface - GET DATA SEGMENT
AX = 7070h
BX = 6060h
CX = 7070h
DX = 7070h
SX = 7070h
DX = 7070h
Return: AX = segment of data structure
Notes: the data structure is at offset 516 from this segment.
the update byte is at offset 514 from this segment. Updates are
once per second while this byte is nonzero and it is decremented
once per second. While this byte is 0 updates are once per minute.
SeeAlso: AX=7070h/BX=7070h
Format of data structure:
Offset Type Description
00h WORD hour
02h WORD minute
04h WORD second
06h WORD day
08h WORD month
0Ah WORD year
0Ch WORD ???
0Eh WORD relative barometric pressure (in 1/100 inches)
10h WORD ???
12h WORD ???
14h WORD temperature 1 (in 1/10 degrees F)
16h WORD temperature 1 lowest (in 1/10 degrees F)
18h WORD temperature 1 highest (in 1/10 degrees F)
1Ah WORD temperature 2 (in 1/10 degrees F)
1Ch WORD temperature 2 lowest (in 1/10 degrees F)
1Eh WORD temperature 2 highest (in 1/10 degrees F)
20h WORD wind speed (in MPH)
22h WORD average of 60 wind speed samples (in MPH)
24h WORD highest wind speed (in MPH)
26h WORD wind chill factor (in 1/10 degrees F)
28h WORD lowest wind chill factor (in 1/10 degrees F)
2Ah WORD ???
2Ch WORD wind direction (in degrees)
2Eh WORD accumulated daily rainfall (in 1/10 inches)
30h WORD accumulated annual rainfall (in 1/10 inches)
----------217070BX7070-----------------------
INT 21 - PCW Weather Card interface - INSTALLATION CHECK
AX = 7070h
BX = 7070h
CX = 7070h
DX = 7070h
SX = 7070h
DX = 7070h
Return: AX = 0070h
BX = 0070h
CX = 0070h
DX = 0070h
SX = 0070h
DX = 0070h
SeeAlso: AX=7070h/BX=6060h,AX=8080h
----------2176-------------------------------
INT 21 - VIRUS - "Klaeren"/"Hate" - INSTALLATION CHECK
AH = 76h
Return: AL = 48h if resident
SeeAlso: AX=6969h,AX=7700h"VIRUS"
----------217761-----------------------------
INT 21 - WATCH.COM v3.2+ - INSTALLATION CHECK
AX = 7761h ('wa')
Return: AX = 6177h
Note: WATCH.COM is part of the "TSR" package by TurboPower Software
SeeAlso: INT 16/AX=7761h
----------217700-----------------------------
INT 21 - VIRUS - "Growing Block" - INSTALLATION CHECK
AX = 7700h
Return: AX = 0920h if resident
SeeAlso: AH=76h,AH=7Fh
----------217F-------------------------------
INT 21 - VIRUS - "Squeaker" - INSTALLATION CHECK
AH = 7Fh
Return: AH = 80h if resident
SeeAlso: AX=7700h,AH=83h"VIRUS"
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