Programming Forums - View Single Post - confused about the usage of Test instruction

Kaja Fumei · Apr 4th, 2006, 11:20 PM

It is a lot like the "cmp" instruction and is often found right before a conditional jump. The difference is the "cmp" instruction uses subtraction to compare them and set the flags while test uses a bitwise AND.

The most common usage of test is to see if a value is 0 or not:

(Toggle Plain Text)

test eax, eax;  eax & eax == 0 only if eax == 0
jz .L1

Apr 4th, 2006, 11:20 PM	#2
Kaja Fumei Hobbyist Programmer Join Date: Oct 2005 Posts: 134 Rep Power: 4	It is a lot like the "cmp" instruction and is often found right before a conditional jump. The difference is the "cmp" instruction uses subtraction to compare them and set the flags while test uses a bitwise AND. The most common usage of test is to see if a value is 0 or not: (Toggle Plain Text) test eax, eax; eax & eax == 0 only if eax == 0 jz .L1 test eax, eax; eax & eax == 0 only if eax == 0 jz .L1