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CAVITE STATE UNIVERSITY
T3 CAMPUS
Department of Information Technology COSC 65 – Programming Languages

 ADD – add second operand to first.
 SUB – Subtract second operand to first.
 CMP – Subtract second operand form first for flags only.
 AND – Logical AND between all bits of two operand. These rules apply:
1 AND 1 = 1
1 AND 0 = 0 As you see, we get 1 only
0 AND 1 = 0 when both bits are 1.
0 AND 0 = 0
.
 TEST – The same as AND but for flags only.
 OR – Logical OR between all bits of two operand. These rules apply:
1 OR 1 = 1
1 OR 0 = 1 As you see, we get 1 every time when
0 OR 1 = 1 at least one of the bits is 1.
0 OR 0 = 0
 XOR – Logical XOR (exclusive OR) between all bits of two operands. These rules apply:
1 XOR 1 = 0
1 XOR 0 = 1 As you see, we get 1 every time when
1 XOR 1 = 1 bits are different from each other.
0 XOR 0 = 0

; Sample code for addition/subtraction Instructions
.model small
.data
.code
main proc
mov cl, 5 ; set 5 as value of cl
add cl, 2 ; add 2 to cl. Can be change to sub for subtraction
endp
end main

; Sample code for cmp or compare Instruction CMP Results ZF CF
.model small Destination < Source 0 1
.data
.code Destination > Source 0 0
Destination < Source 1 0
main proc
mov ax, 500 ; set value of ax as 500
mov bx, 200 ; set value of bx as 200

cmp ax, bx ; cmp (ax – Destination) (bx – Source)
endp

end main To check what’s happening in this code:
1. Compile the load the emulator
2. click single step and check what’s happening per
line of code.
3. Repeat single step process 3 times.
4. Then click the flag button to see the CMP Results.
5. CF and ZF must be 0.
6. Try to change the value of ax and bx. Then repeat
the same process and check what will be the result.

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