ZBGTIP.DOC

George W. Flanders
[73300,2272]

	I have been working (often struggling) with Radio Shack's ZBGASM.CO 
Model 100 assembler for some time, and have found that one annoying aspect of 
the program is its requirement that text strings be enclosed by delimiters; and,
if you follow the RS's sample, when the string is to be printed one is told to 
utilize a counter register to terminate a printing loop you can write yourself.
	That might be good practice, but it makes for additional and unnecessary
coding. In addition to some other ROM routines which print a buffer until they 
encounter a null, a routine starting at 27B1H (10161D) has been reported by 
Robert D. Covington in his ROM disassembly on the SIG. It prints the buffer 
pointed to by HL until it encounters a null _OR_ CHR$(34) ("). This information 
allows us to simply add end quotes to the string inside the closing delimiter, 
thereby avoiding the need to store a null at the end of each string (or using up
precious bytes with a silly counter/print loop).
	Formerly, a string in ZBGASM format might have looked like this:
	GRTNG:	DC	\Hello\
and we would have had to load a counter register with 05H when printing the 
string. Now, we can simply add the quotes:
	GRTNG:	DC	\Hello"\
point HL (LXI H,GRTNG or any other symbol we'd like to use), and call 27B1H when
we're ready to print the string. This may not seem like a big deal, but it saves
bytes and trouble.
	Interestingly enough, this works in BASIC, too, although it's hard to 
imagine why anyone would go to all the trouble of poking an ASCII string 
somewhere in memory terminated by a quote and then CALLing it from the program. 
Anyway, the form would be "CALL10161,0,addr", which loads a null in the 
accumulator (it wouldn't matter much what you put there) and points HL to the 
starting address of the string in memory terminated with chr$(34). If you'd like
to try it, run the following little program:
	0 A=0
	1 FORI=57000TO57005
	2 READD:POKEI,D:NEXT
	3 POKE63093,A
	4 CALL10161,0,57000
	5 DATA72,101,108,108,111,34
Changing line 0 to read "A=1" makes the output device the printer (1) instead of
the screen (default=0). Obviously, in machine code you could change the output 
device the same way:
	MVI	A,01H
	STA	0F675H
before calling the routine.