Question

i’m beginning assembly, i’m using nasm for assembling the code,
i’m trying to process a string residing in memory and change it,
i want to check if a byte is in a certain range (ascii) so i can decide what to do with it,
i can’t seem to figure how to check if a value is in a certain range, i know all about
the different kind of jump flags but how can i combine 2 cmp statements ?

my question is :
how do i produce something similiar to this in assembly ?

if (x>=20 && x<=100)
     do something

thanks alot !

Answer 1

Depending on what syntax you’re using, and assuming x is in the eax register, something like this:

cmp  eax, 20
jl   ELSE
cmp  eax, 100
jg   ELSE
#do something
jmp  END

ELSE:
#do else

END: