DU-V77.DOC
               by Ward Christensen
 with additional notes by Ron Fowler and Keith Petersen
                (revised 7/23/81)

       HOW TO USE DU ver 7.7 DISK UTILITY

INSTALLATION:
       The 7.0 and later versions of DU are designed to
 be installed with a minimum of trouble.  In fact, in al-
 most all cases, no changes to the source file should be
 necessary to get DU up and running. This is because DU
 uses the disk paramter block of CP/M to determine the
 characteristics of the disk environment.  (see the dis-
 claimer for certain non-standard versions of CP/M 1.4).
       The only parameter that should need to be changed
 will be the clock speed flag at 103H.  Leave this byte
 zero if you have a 2 mhz clock.  Patch it non-zero for
 4 mhz.  This is only needed for the "Z" (sleep) command.

USE:

Any valid command string may be placed as an
operand of the original DU command, i.e.:

    A>DU G0;D;G2;=OK<D><A><1A>;D

Functions supported:

       Tnn     Seek to track nn (no read)
       Snn     Position to sector nn, and read
       Gnn     Position to group nn and read.
       G       Shows current position
       V       Views the current sector.
               (assumes ASCII data)
       Vnn     Views nn sectors
       Fname   print directory for file "name",
               then positions to its directory
               sector. (Won't position under
               CP/M 2.x, but see = command below.)

       =string Ascii search, starting at current
               sector. <xx> hex may be imbedded,
               or used alone:  To find "IN 0FEH":
               =<db><fe>
               Ignores bit 7 unless <xx> is used.

       L       Re-logs in the current disk. You may pull
               out a disk, put in a new, and "L" just
               to log it in.

       Lx      Logs in disk 'x', such as: LB

       Ux      Logs user 'x' for next F command.  Gives
               '?' error if not CP/M version 2.x.

       D       Dump sector, hex + ASCII
       A       Dump sector, ASCII only
       H       Dump sector, hex only

note all dump commands (D, A, H) may be optionally
       followed by a starting and ending address:
       D0,7F   is the same as just D
       D3,5
       A20,3F

       CHaddr,val,val,val... change hex in sector
       CAaddr,char string... change ASCII in sector
               NOTE that <xx> may be hex imbedded
               in the Ascii:  ca0,OK<d><a><1a>

               ----> Use W to write changes to disk.
               Note that the C command echoes
               the overlaid data for verification.

       CHaddr-addr,byte
or     CAaddr-addr,byte        repeats a change

       +       advance 1 sector (if below track 2,
               this advances to next numerical, if
               2 or >, advances based on CP/M's normal
               sector scrambling algorithm, i.e. so +
               will get the next logical sector of the file

       -       backs up 1 logical sector

               Note + and - may take an amount:
               for example, +F steps in 15 sectors.

               Note also that "-" issued at the first logical
               sector of the disk will wrap back to the last.
               Further, "+" issued at the last sector will
               wrap forward to the first.

       ?       Gives command summary

       #       Prints the disk parameters

       M       Dumps a map of the group allocations
               for files.
       Mn      Shows which file is allocated to
               group "n".

       N       Resets CP/M via the BDOS.  This may
               make it possible under some implementations
               of CP/M to change the disk format (e.g., density,
               sides, etc)

       R       Reads the sector currently positioned to
               into memory.  Note R (Read) is implicit in
               the G, +, and - commands, but N-O-T in the
               S and T commands (I did it because I was
               tired of disk reading after T command before
               I had a chance to issue the S command)

       W       Write back the current sector (N-O-T-E may
               not be used after an F command, as CP/M was
               used to find the file in the directory

       X       Exit back to CP/M (Must press return).  Ctl-c
               was too easy to hit over modem lines, so I
               decided on 2-byte (X, CR) to exit.

       P       Toggle printer switch on/off

       Y       Yanks current sector into sequential memory and
               prints ending address.  This allows sectors to
               be written sequentially into memory starting at
               3000H, for later recovery by DDT, etc.

       Z       Sleep - causes the program to pause, such
               as to look at a dump.  Z is 1 sec.  Znn
               is nn tenths of a second on a 2 MHz 8080.

       <       Saves current sector in a save buffer

       >       Gets saved buffer.  < and > may be used
               to move a sector to another place.

       /       Repeats entire command.  Defaults
or     /nn     to "forever".  NN may be 2 to 65535

multiple commands may be separated by ";"

Example: the following commands will erase the
        b disk directory to all E5's:

       lb              log in b drive
       g0              position to dir.
       ch0-7f,e5       fill with e5
       <               save the sector
       >;w;+;/16       restore, write, next,
                       repeat 16

----This could be shortened to:

       lb;g0;ch0-7f,e5;<
       >;w;+;/16



INTERPRETATION OF DIRECTORY DATA PRESENTED BY THE DU PROGRAM


The following explains the format of a CP/M directory entry
as shown by DU, using either the "F" (find file) command,
or just doing "D" (dump) of the directory sectors, which
are located in groups 0 and 1 on a single density disk.
               ----------------
Sample result of "FSID.COM" command:

40  00534944 20202020  20434F4D 0000003A  *.SID     COM...:*
50  33343536 3738393A  00000000 00000000  *3456789:........*

First line -

40  00534944 20202020  20434F4D 0000003A  *.SID     COM...:*
||  |||                      |  ||    ||    |         |
||  ||^----hex file name-----^  ||    ||    ^file name^
||  ||                          ||    ||     in ASCII
||  ||                   extent-^^    ||
||  ||                                ||
||  ||           file size in sectors-^^
||  ||
||  ^^-00 = file active
||     E5 = file erased
^^-displacement of line in directory sector

Second line -

50  33343536 3738393A  00000000 00000000  *3456789:........*
   |                                  |
   |                                  |
   ^---allocation group numbers-------^

END

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