Microprocessors Questions and Answers – Instruction Set of 8086/8088 – 1

This set of Microprocessor Multiple Choice Questions & Answers (MCQs) focuses on “Instruction Set of 8086/8088 – 1”.

1. The instruction that is used to transfer the data from source operand to destination operand is
a) data copy/transfer instruction
b) branch instruction
c) arithmetic/logical instruction
d) string instruction
View Answer

Answer: a
Explanation: These instructions are used to copy and transfer the instructions.

2. Which of the following is not a data copy/transfer instruction?
a) MOV
b) PUSH
c) DAS
d) POP
View Answer

Answer: c
Explanation: DAS (Decimal Adjust after Subtraction) is an arithmetic instruction.

3. The instructions that involve various string manipulation operations are
a) branch instructions
b) flag manipulation instructions
c) shift and rotate instructions
d) string instructions
View Answer

Answer: d
Explanation: The string instructions perform operations on strings such as load, move, scan, compare etc.
advertisement
advertisement

4. Which of the following instruction is not valid?
a) MOV AX, BX
b) MOV DS, 5000H
c) MOV AX, 5000H
d) PUSH AX
View Answer

Answer: b
Explanation: Both the source and destination operands cannot be memory locations except for string instructions.

5. In PUSH instruction, after each execution of the instruction, the stack pointer is
a) incremented by 1
b) decremented by 1
c) incremented by 2
d) decremented by 2
View Answer

Answer: d
Explanation: The actual current stack-top is always occupied by the previously pushed data. So, the push operation decrements SP by 2 and then stores the two bytes contents of the operand onto the stack.
Note: Join free Sanfoundry classes at Telegram or Youtube

6. The instruction that pushes the contents of the specified register/memory location on to the stack is
a) PUSHF
b) POPF
c) PUSH
d) POP
View Answer

Answer: c
Explanation: Since PUSH operation transfers data to stack from a register or memory location.

7. In POP instruction, after each execution of the instruction, the stack pointer is
a) incremented by 1
b) decremented by 1
c) incremented by 2
d) decremented by 2
View Answer

Answer: c
Explanation: The actual current stack top is poped into the specific operand as the contents of stack top memory is stored in AL&SP and further contents of the memory location pointed to by SP are copied to AH & SP.
advertisement

8. The instructions that are used for reading an input port and writing an output port respectively are
a) MOV, XCHG
b) MOV, IN
c) IN, MOV
d) IN, OUT
View Answer

Answer: d
Explanation: The address of the input/output port may be specified directly or indirectly.
Example for input port: IN AX, DX; This instruction reads data from a 16-bit port whose address is in DX and stores it in AX
Example for output port: OUT 03H, AL; This sends data available in AL to a port whose address is 03H.

9. The instruction that is used for finding out the codes in case of code conversion problems is
a) XCHG
b) XLAT
c) XOR
d) JCXZ
View Answer

Answer: b
Explanation: The translate(XLAT) instruction is used to find codes.
advertisement

10. The instruction that loads effective address formed by destination operand into the specified source register is
a) LEA
b) LDS
c) LES
d) LAHF
View Answer

Answer: a
Explanation: The instruction, LEA loads effective address and is more useful for assembly language rather than for machine language.

11. The instruction that loads the AH register with the lower byte of the flag register is
a) SAHF
b) AH
c) LAHF
d) PUSHF
View Answer

Answer: c
Explanation: The instruction LAHF(Load AH from a lower byte of Flag) may be used to observe the status of all the condition code flags(except overflow flag) at a time.

12. The instruction that pushes the flag register on to the stack is
a) PUSH
b) POP
c) PUSHF
d) POPF
View Answer

Answer: c
Explanation: The instruction PUSHF(push flags to stack) pushes the flag register on to the stack.

13. The instruction that loads the flag register completely from the word contents of the memory location is
a) PUSH
b) POP
c) PUSHF
d) POPF
View Answer

Answer: d
Explanation: POPF is pop flags to stack.

14. The instruction that adds immediate data/contents of the memory location specified in an instruction/register to the contents of another register/memory location is
a) SUB
b) ADD
c) MUL
d) DIV
View Answer

Answer: b
Explanation: ADD instruction adds the data.

15. The instruction that supports addition when carry exists is
a) ADD
b) ADC
c) ADD & ADC
d) None of the mentioned
View Answer

Answer: b
Explanation: ADC(Add with Carry) instruction performs the same operation as ADD operation, but adds the carry flag bit to the result.

Sanfoundry Global Education & Learning Series – Microprocessors.

Here’s the list of Best Books in Microprocessors.

To practice all areas of Microprocessors, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.