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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