When I write this:
mov cx,dh
mov dx,dl
It makes an error:
invalid combination of opcode and operands
I'm a beginner at assembly language so I need help!
CodePudding user response:
mov cx,dh
The error message you get for mov cx, dh
means that the size of the CX destination register (16 bits) is different from the size of the DH source register (8 bits). For most instructions, operands must be the same size.
There are several ways to copy DH in CX.
unsigned signed
-------- ------
1) movzx cx, dh 1) movsx cx, dh ; 386
2) mov ch, dh
sar cx, 8
2) mov cl, dh 3) mov al, dh ; 8086
mov ch, 0 cbw
mov cx, ax
3) xor cx, cx 4) mov ah, dh
mov cl, dh mov cl, 8
sar ax, cl
mov cx, ax
There are several ways to copy DL in DX.
unsigned signed
-------- ------
1) movzx dx, dl 1) movsx dx, dl ; 386
2) mov dh, dl
sar dx, 8
2) mov dh, 0 3) mov al, dl ; 8086
cbw
mov dx, ax
4) mov dh, dl
mov cl, 8
sar dx, cl
Choose wise and stick with the simple ones!