Chapter-5 ARITHMETIC AND LOGIC INSTRUCTIONS UET Taxila COMPUTER MISC

CHAPTER NO 5
ARITHMETIC AND LOGIC INSTRUCTIONS
1. Select an ADD instruction that will:
(a) add BX to AX
(b) add 12H to AL
(c) add EDI and EBP
(d) add 22H to CX
(e) add the data addressed by SI to AL
(f) add CX to the data stored at memory location FROG
(g) add 234H to RCX
A. (a) ADD AX,BX (b) ADD AL,12H (c) ADD EBP,EDI (d) ADD CX,22H (e) ADD AL,[SI]
(f) ADD FROG,CX (g) ADD RCX,234H
2. What is wrong with the ADD RCX,AX instruction?
A. You cannot use mixed-size registers
3. Is it possible to add CX to DS with the ADD instruction?
A. No instruction is available to add to a segment register.
4. If and , list the sum and the contents of each flag register bit
(C, A, S, Z, and O) after the ADD AX,DX instruction executes.
A. AX = 3100H, C = 0, A = 1, S = 0, Z = 0, and O = 0
5. Develop a short sequence of instructions that adds AL, BL, CL, DL, and AH. Save the sum
in the DH register.
A. ADD AH,AL
ADD AH,BL
ADD AH,CL
ADD AH,DL
MOV DH,AH
6. Develop a short sequence of instructions that adds AX, BX, CX, DX, and SP. Save the sum
in the DI register.
A. ADD AX,BX
ADD AX,CX
ADD AX,DX
ADD AX,SP
7. Develop a short sequence of instructions that adds ECX, EDX, and ESI. Save the sum in
the
EDI register.
A. MOV EDI,ECX
ADD EDI,EDX
ADD EDI,ESI
8. Develop a short sequence of instructions that adds RCX, RDX, and RSI. Save the sum in
the
R12 register.
A. MOV DI,AX
MOV R12,RCX
ADD R12,RDX
ADD R12,RSI
9. Select an instruction that adds BX to DX, and also adds the contents of the carry flag (C)
to
the result.
A. ADC DX,BX
10. Choose an instruction that adds 1 to the contents of the SP register.
A. INC SP
11. What is wrong with the INC [BX] instruction?
A. he instruction does not specify the size of the data addressed by BX and can be
corrected with a BYTE PTR, WORD PTR, DWORD PTR, or QWORD PTR
12. Select a SUB instruction that will:



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, CHAPTER NO 5
ARITHMETIC AND LOGIC INSTRUCTIONS
(a) subtract BX from CX
(b) subtract 0EEH from DH
(c) subtract DI from SI
(d) subtract 3322H from EBP
(e) subtract the data address by SI from CH
(f) subtract the data stored 10 words after the location addressed by SI from DX
(g) subtract AL from memory location FROG
(h) subtract R9 from R10
A. (a) SUB CX,BX (b) SUB DH,0EEH (c) SUB SI,DI
(d) SUB EBP,3322H (e) SUB CH,[SI] (f) SUB
DX,[SI+10] (g) SUB FROG,AL (h) SUB R10,R9
13. If and , list the difference after BH is subtracted from DL and show
the contents of the flag register bits.
A. L = 81H, S = 1, Z = 0, C = 0, A = 0, P = 0, O = 1
14. Write a short sequence of instructions that subtracts the numbers in DI, SI, and BP from
the
AX register. Store the difference in register BX.
A. MOV BX,AX
SUB BX,DI
SUB BX,SI
SUB BX,BP
15. Choose an instruction that subtracts 1 from register EBX.
A. DEC EBX
16. Explain what the SBB [DI–4],DX instruction accomplishes.
A. he contents of DX and the carry flag are subtracted
from the 16-bit contents of the data segment memory
addressed by DI – 4 and the result is placed into DX.
17. Explain the difference between the SUB and CMP instruction.
A. Both instructions subtract, but compare doe not return the difference, it only
changes the flag bits to reflect the difference.
18. When two 8-bit numbers are multiplied, where is the product found?
A. AH (most significant) and AL (least significant)
19. When two 16-bit numbers are multiplied, what two registers hold the product? Show the
registers that contain the most and least significant portions of the product.
A. AH contains the most significant part of the result and AL contains the least
significant part of the result
20. When two numbers multiply, what happens to the O and C flag bits?
A. The O and C flags contain the state of the most significant portion of the product. If the
most significant
part of the product is zero, then C and O are zero
21. Where is the product stored for the MUL EDI instruction?
A. DX and EAX as a 64-bit product
22. Write a sequence of instructions that cube the 8-bit number found in DL. Load DL with a
5 initially, and make sure that your result is a l6-bit number.
DL = 0F3H BH = 72H
AX = 1001H DX = 20FFH
190
A. MOV DL,5
MOV AL,DL
MUL DL
MUL D
23. What is the difference between the IMUL and MUL instructions?



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