Compare

Assembly Language Programming 7

Compare

The 'Compare' Instruction is

CMP destination,source

This instruction 'pretends' to subtract the source from the destination, and sets the flags as if it had done so, but does not in fact alter the number in the register.

Example

MOV	AL,65
CMP	AL,65

This program would set the Zero flag

Another Example.

A program which inputs a sequence of characters, until the 'Enter' key is pressed.

	MOV	AH,1	{Initialise interrupt for Input}
@loop	INT	21H	{Input a character into AL}
	CMP	AL,13	{Is character a carriage return?}
	JNZ	@loop	{If not, then go and input another}