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MCQ | Addressing Modes in 8086 Microprocessor

Multiple choice questions and answers (MCQ) based on the various addressing modes of the 8086 microprocessor with 4 choices, correct answer and explanation.
Submitted by Monika Sharma, on September 01, 2019

Question 1:

You are given the following instruction:
ADD AX , [1024]
You are provided the following data:
DS = 3423H ; SS = 1234H ; CS= 4567H
Find the effective address location for the given instruction.

  1. 35254 H
  2. 13364 H
  3. 46694 H
  4. 4447 H

Answer: a. 35254 H

Explanation:

The address is directly mentioned in the instruction. So, The Data Segment Register will be used as the segment for the given offset address value. Hence the effective address is:

    =   3423H X 10H + 1024H
    = 	34230H + 1024H
    = 	35254H

Question 2:

Which segment register is being used in the given instruction?
MOV CX , SS: [BX]

  1. Extra Segment Register (ES)
  2. Code Segment Register (CS)
  3. Stack Segment Register (SS)
  4. None of the Above

Answer: c. Stack Segment Register (SS)

Explanation:

Here, the concept of Segment Override Prefix is being used. Although the default segment for the offset BX is DS, as the SS is mentioned in the instruction, it is overriding the default segment. Hence, the Stack Segment (SS) register is being used here.


Question 3:

You are given the following instruction:
MOV AX , 02H [BX] [SI]
and are provided the following data:
DS = 3290H ; SS = 1004H ; ES= 4237H ; BX= 1100H ; SI= 1101H
Find the effective address location for the given instruction.

  1. 35254 H
  2. A234F H
  3. 34B03 H
  4. 4447E H

Answer: c. 34B03 H

Explanation:

The address is mentioned in the instruction contains register BX and SI with 8-bit displacement. So, The Data Segment Register (DS) will be used as the segment for the given offset address value. Hence the effective address is:

    Effective Address	=	3290H X 10H + ( 02H + 1100H + 1101H )
                        = 	329000H + 2203H
                        = 	34B03H

Question 4:

Which segment register is being used in the given instruction?
MOV CX , [IP]

  1. Extra Segment Register (ES)
  2. Code Segment Register (CS)
  3. Stack Segment Register (SS)
  4. None of the Above

Answer: c. Stack Segment Register (SS)

Explanation:

Here, the default segment for the offset IP is SS. Hence, the Stack Segment (SS) register is being used here.


Question 5:

Which addressing mode is being used in the given instruction?
MOV AX, [1234H]

  1. Base Addressing Mode
  2. Immediate Addressing Mode
  3. Register Addressing Mode
  4. Direct Addressing Mode

Answer: d. Direct Addressing Mode

Explanation:

The given instruction is using the direct addressing mode as the address is directly mentioned in the instruction rather than being stored in any register.






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