4.2 Arithmetic Instructions Addition instructions: ADD, ADC, INC ,AAA, DAA ADD, ADC INC CF 0 Initial AL: 0110 1001+ AF1 Initial BL: 0100 1000 Because: 1011>1001 AF=1 AL after ADD: 1011 0001 + AAA,DAA DAA: 0110 0110 CF 1 AL after DAA: 0001 0111 AF1 Example: BCD addition: ADD AL, BL AL after clear: 0000 0000+ CF 0 supposing: BH=29H BL=48H AL=69H DAA Initial BH: 0010 1001 AF 0 MOV BL, AL Carry Flag: 1 MOV AL, 0 Because: CF=0,0010<1001 1010>1001 2948+ 69 + ADC AL, BH AL after ADC: 0010 1010 DAA DAA: 0000 0110 3017 MOV BH, AL AL after DAA: 0011 0000

4.2 Arithmetic Instructions Subtraction instructions: SUB, SBB, DEC, NEG, AAS, DAS SUB, SBB, CMP SF 1 DEC, NEG CF 1 Initial AL: 0100 1000- AF1 Initial BL: 0110 1001 Because: CF,1101>1001 AF,1111>1001 AL after SUB: 1101 1111 - AAS,DAS DAS: 0110 0110 CF 1 AL after DAS: 0111 1001 AF 1 Example: BCD addition: SUB AL, BL AL after update: 0010 1001- CF 0 supposing: AH=29H AL=48H BL=69H DAS Subtractor: 0000 0000 AF 0 MOV BL, AL Carry Flag: 1 MOV AL, AH Because: CF=0,0010<1001 AF=0,1000<1001 2948- 69 - SBB AL, 0 AL after SBB: 0010 1000 DAS DAS: 0000 0000 2879 MOV BH, AL AL after DAS: 0010 1000

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

4.2 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

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 = 0010 0101B CL = 55H = 0101 0101B AND AL,CL TEST AL,CL AL05H=0000 0101B SF0; ZF0; PF1; AL25H=0010 0101B SF0; ZF0; PF1; BSF, BSR supposing: EAX = 0000 0000 0111 1111 0000 0000 0000 0000B BSF, BSR BSF EBX, EAX BSR EBX, EAX EBX 10H EBX 16H

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

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.