A small script that simply prints a given string. It's an improved snippet that combines some recommendations given in my post on string helper functions.
org 100h
mov si, hello
call puts
ret
puts:
jmp .run
.putc:
mov ah, 0Eh
mov bx, 7
int 10h
.run:
lodsb
cmp al, 0
jne .putc
ret
hello db "Hello World!", 0
You have all the elements. The only thing that can be eliminated is jmp .run, as follows:
org 0x100
mov si, Prompt
call puts
ret
puts: mov ah, 0xe
mov bx, 7
.read: lodsb
or al, al
jnz .post
ret
.post: int 0x10
jmp .read
Prompt: db 'Hello World', 0
As INT 10H does not trash AH or BX, there is no need to reinitialize them each time through the loop.
TEST reg, reg to check for zero in preference to OR reg, reg, since the former is more likely to fuse with the conditional branch. I also find it more readable.
\$\endgroup\$
Commented
Nov 16, 2019 at 4:33
test is more representative of what is being done and I think that's what you mean by more readable. Whereas or implies AL is being modified for some other reason.
\$\endgroup\$
Commented
Nov 16, 2019 at 7:58
trashing in the context that a register has been modified by an interrupt, function or subroutine where its value upon return is indeterminate. As to the reference your using, I think it would be safe to say that if nothing is returned, then nothing is modified either or it specifically states returned values.
\$\endgroup\$
Commented
Nov 16, 2019 at 17:42