Question

I’m using MASM.

I’d like to check the second (and third) character of a String in assembly.

I tried this:

; String is in DWORD operandA
mov eax, OFFSET operandA+1
cmp eax, '!'
je Fact

This doesn’t work. Any advice?

Answer 1

you’d need to dereference the pointer to get the actual character:

mov eax, OFFSET operandA+1
mov cl,byte ptr [eax]
cmp cl,'!'

or

mov eax, OFFSET operandA
mov cl,byte ptr [eax + 1]
cmp cl,'!'

this preserves eax so you can compare the second char using:

inc eax
mov cl,byte ptr [eax]
cmp cl,'?'

or

mov cl,byte ptr [eax + 2]
cmp cl,'?'