1. 4.2 Arithmetic Instructions
Addition instructions: ADD, ADC, INC ,AAA, DAA
ADD, ADC
INC
CF 0
Initial AL:
AF1
Initial BL:
Because: 1011>1001
AF=1
AL after ADD: +
AAA,DAA
DAA:
CF 1
AL after DAA:
AF1
Example:
BCD
addition:
ADD AL, BL
AL after clear:
CF 0
supposing:
BH=29H
BL=48H
AL=69H
DAA
Initial BH:
AF 0
MOV BL, AL
Carry Flag:
MOV AL, 0
Because: CF=0,0010<1001
1010>1001
2948+ 69 +
ADC AL, BH
AL after ADC:
DAA
DAA:
3017
MOV BH, AL
AL after DAA:

2. 4.2 Arithmetic Instructions
Subtraction instructions: SUB, SBB, DEC, NEG, AAS, DAS
SUB, SBB, CMP
SF 1
DEC, NEG
CF 1
Initial AL:
AF1
Initial BL:
Because: CF,1101>1001
AF,1111>1001
AL after SUB: -
AAS,DAS
DAS:
CF 1
AL after DAS:
AF 1
Example:
BCD
addition:
SUB AL, BL
AL after update:
CF 0
supposing:
AH=29H
AL=48H
BL=69H
DAS
Subtractor:
AF 0
MOV BL, AL
Carry Flag:
MOV AL, AH
Because: CF=0,0010<1001
AF=0,1000<1001
2948- 69 -
SBB AL, 0
AL after SBB:
DAS
DAS:
2879
MOV BH, AL
AL after DAS:

3. 4.2 Arithmetic Instructions
Multiplication instructions: MUL, IMUL, AAM
MUL, IMUL
IMUL additional, 2 operands
Examples:
signed and unsigned multiplication:
AAM
supposing:
AL = FFH = -1(2’sC)
CL = FEH = -2(2’sC)
IMUL additional, 3 operands
MUL CL
IMUL CL
AXFD02H
AX0002H

4. 4.2 Arithmetic Instructions
Division and conversion instructions: DIV, IDIV, AAD, CBW, CWD
DIV, IDIV
CBW
AAD
CWD
CWD
CWDE
Examples:
multiplying AL by CX (signed values):
supposing:
AL = FFH = -1(2’sC)
CX = FFFEH = -2(2’sC)
CBW
Convert byte FFH to word FFFFH in AX
IMUL CX
Multiplying words AX and CX

5. 4.3 Logical Instructions AND, OR, XOR, TEST, NOT BSF, BSR Examples:
difference between AND and TEST:
AND, OR, XOR, TEST
NOT
supposing:
AL = 25H = B
CL = 55H = B
AND AL,CL
TEST AL,CL
AL05H= B
SF0; ZF0; PF1;
AL25H= B
SF0; ZF0; PF1;
BSF, BSR
supposing:
EAX = B
BSF, BSR
BSF EBX, EAX
BSR EBX, EAX
EBX 10H
EBX 16H

6. 4.3 Logical Instructions BT, BTC, BTS, BTR BT, BTC, BTS, BTR Example:
MOV AX,5555H ;AX=5555,CF=0
BT AX,10 ;AX=5555,CF=1
BT AX,11 ;AX=5555,CF=0
MOV BX,10
BTC AX,BX ;AX=5155,CF=1
INC BX
BTS AX,BX ;AX=5955,CF=0
BTR AX,0 ;AX=5554,CF=1

7. 4.3 Logical Instructions SETcc
The terms “less” and “greater” are used for comparisons of signed integers.
The terms “above” and “below” are used for comparisons of unsigned integers.