Unknown 8085 opcodes

Fred Cisin cisin at xenosoft.com
Thu Jan 12 15:01:46 CST 2017


>> 		jsr	puts
>> 		fcc	'Hello, world!',13,0
>> 		clra
or the classic:
    JMP START1
    DATA2:	DB . . .
         	DB . . .
    START1: MOV DX, OFFSET DATA2 
Which was heavily used because
    MOV DX, OFFSET DATA3
    . . .
    DATA3: DB . . .
would pose "forward reference" or "undefined symbol" problems for some 
assemblers.

Even for manual assembly, or 'A' mode of DEBUG.COM, it was handy to 
already know the address of the data before you wrote the steps to access 
it.

On Thu, 12 Jan 2017, Mouse wrote:
> Mine can't do that automatically, but it can with a little human
> assist; the human would need to tell it that the memory after the jsr
> is a NUL-terminated string, but that's all it would need to be told.

Not all strings are null-terminated.  In CP/M, and MS-DOS INT21h Fn9, the 
terminating character is '$' !
"If you are ever choosing a termination marker, choose something that 
could NEVER occur in normal data!"
Also, strings may, instead of a terminating character, be specified with a 
length, or with a start and end address.




More information about the cctech mailing list