Patch points in DBASE 2.41
                                              Naj Najarian
                                              Kempton, PA 19519
                                              6 March 1989

Before I came across Bruce Morgan's DBCLOCK routine to let DBASE
get the date from DateStamper, in fact, before I even ran
DateStamper, I used an alias to let DBASE get the date (but not
the time) from ZCPR, providing that I set the date at cold boot.

Before I got ZSDOS, before I used DateStamper, before I had a
computer with a clock (!), I used to store the current date in
the registers for use by me or any other program I could get to
read them.  I'd set the date on power-up with a simple REG S1
06;REG S2 03;REG S3 89 (I couldn't use register #0, because other
programs take possession of it and store results there.  Other
programs require register #9.  Luckily progammers tend to leave
1-8 alone.  Please note that I also store the date in European
form. You may have to change the alias for your own preference.)
As Jay improved ARUNZ, I could make the system prompt me for the
date a little more politely.

But I had to find a way to get the numbers from the registers and
into DBASE in a form it would understand.  I found where DBASE
stores the date ($44ff thru $4501) and could poke the date into
those places from the registers, but unless I ran a command file
from the commandline, DBASE would refuse to recognize that it
already knew the date.  I had to find a way to tell it NOT to ask
for the date.

So a little Z8E-ing, and I found out which bites to change (see
below for the disassembly).  My script simply converts the date
to hexadecimal form (thus the need for hard-coding the addresses
of the registers in memory), pokes those values into DBASE
the current date, and tells it skip over the routine to verify
the date.  Looks like this:
                                                            jump over the date-checking routine
                              where dbase stores the date           |
              dbase renamed            |    date from registers in hex (DANGER! Hard-coded for my system)
                       |               |      |                     |
                       V               V      V                     V
DO=DBASE  get 100 a2:dbase241.com;poke 44ff $mhecb1 $mhecb2 $mhecb3;poke 491b c3 ff 49;go $1;

And it works whether or not you give it a command file to run (cf
DBASE versus DBASE MAKORDER).  It's faster than DBCLOCK, and I
don't have to remember to insert the command into all my *.CMD
files.  It always runs.  Sole caveat: now that we have NZ-COM,
the address of the registers in memory could vary depending on
the system we running at the time of the call.


While I'm at it, let me document a few other patch points in
DBASE 2.41, and I'll put out a query too: does anyone know of a
DBASE equivalent of WSBible or Ted Silvera's oft repeated
Profiles article?


             PATCH BYTES IN DBASE.COM version 2.41

0160   form of date:
      00 for American MM/DD/YY
      FF for European DD/MM/YY

015D   error correction
      00 if you don't want chance to correct mistakes
      FF if you want to be prompted for correction every time
         you enter an error

30A0   name of alternate file when recording screen output to
      disk.  In the form THISFILE.TXT.  The dot twixt filename
      and extension is necessary

44FF   day in hex if European, month if American

4500   month in hex if European, day if American

4501   hex for last two digits of year (e.g. 1989 would be $59)

450B   logged drive (0=A, 1=B, etc.)

4502   BELL (as adjusted by using SET BELL OFF)
      00 for off
      FF for on

4505   CARRY (as adjusted by using SET CARRY OFF)
      00 for off
      FF for on

4508   COLON (as adjusted by using SET COLON OFF)
      00 for off
      FF for on

4509   CONFIRM (as adjusted by using SET CONFIRM OFF)
      00 for off
      FF for on

442F   CONSOLE (as adjusted by using SET CONSOLE OFF)
      00 for off
      FF for on

450A   DEBUG (as adjusted by using SET DEBUG OFF)
      00 for off
      FF for on

450C   DELETE (as adjusted by using SET DELETED OFF)
      00 for off
      FF for on

451F   ECHO (as adjusted by using SET ECHO OFF)
      00 for off
      FF for on

452B   EJECT (as adjusted by using SET EJECT OFF)
      00 for off
      FF for on

4521   ESCAPE (as adjusted by using SET ESCAPE OFF)
      00 for off
      FF for on

4522   EXACT (as adjusted by using SET EXACT OFF)
      00 for off
      FF for on

4526   INTENSITY (as adjusted by using SET INTENSITY OFF)
      00 for off
      FF for on

4529   LINKAGE (as adjusted by using SET LINKAGE OFF)
      00 for off
      FF for on

452E   TALK (as adjusted by using SET TALK OFF)
      00 for off
      FF for on

; documentation on disassembled DBASE II 2.41 code
; particularly the date startup operations and mods
; made to my daily use edition.
;
; 17 May 1988
;
;
491B    xor     a               ; get a zero
                               ; it's this I changed to jp 49ff
                               ; which avoids the user input altogether
                               ; because I have ZCPR poke in the date
                               ; before running dBase
491C    ld      (44ff),a        ; stick it in DD
       ld      (4500),a        ; null out MM
       ld      (4501),a        ; null out YY
4925    ld      a,76            ; ?
       call    3c0b            ; ?? (is that called address right, too?)
492A    ld      a,(0160)        ; month first flag
       or      a
492E    jz      493a            ; go there on American dating system
4931    ld      h,4b48          ; point to ' (DD/MM/YY) '
4934    call    36c5            ; print it
4937    jp      4940
493A    ld      h,4b56          ; point to ' (MM/DD/YY) '
493D    call    36c5            ; print it
4940    call    3a35            ; get date from user
4943    call    3a0f            ; check it for unacceptable values
4946    jz      49ff            ; jump if date is ok
4949    call    3899            ; uh-oh, bad date



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