Engineering Questions with Answers - Multiple Choice Questions

MCQs on Special Operations

1 - Question

Which of the following operation is not carried out by 80286?
a) task switch operation
b) halt
c) processor reset
d) none of the mentioned

View Answer

Answer: d
Explanation: The 80286 carries out six operations. They are:
1. processor reset and initialization
2. task switch operation
3. pointer testing instructions
4. protected mode initialization
5. how to enter protected mode?
6. halt.




2 - Question

After completion of the first cycle, the first task is again scheduled for the next cycle. This process is known as
a) repetition
b) task switch operation
c) processor initiation
d) none of the mentioned

View Answer

Answer: b
Explanation: After completion of the first cycle, the first task is again scheduled for the next cycle, and the process continues. The previous task that was incomplete, may be completed during its coming turns of the allotted CPU time slice. This switch-over operation from one task to another is called task switch operation.




3 - Question

The operation that is provided by the internal architecture, to save the execution state of a task is
a) processor reset
b) processor initialization
c) task switch operation
d) halt

View Answer

Answer: c
Explanation: The 80286 internal architecture provides a task switch operation, to save the execution state of a task, and to load a new task to be executed.




4 - Question

The instruction that can be used to carry out task switch operation is
a) software interrupt instruction
b) exception
c) external interrupt
d) all of the mentioned

View Answer

Answer: d
Explanation: A software interrupt instruction, exception or external interrupt, can also be used to carry out task switch operation.




5 - Question

The IRET instruction gets back the execution state of the previous task, if
a) NT (nested task flag) = 1
b) NT (nested task flag) = 0
c) IF (interrupt flag) = 1
d) IF (interrupt flag) = 0

View Answer

Answer: a
Explanation: If NT = 1, the IRET instruction gets back the execution state of the previous task. Otherwise, the IRET instruction lets the current task continue, after popping the required values from the stack.




6 - Question

The NT flag is set by the task switch operation, that is initiated by
a) CALL
b) INT
c) CALL & INT
d) None of the mentioned

View Answer

Answer: c
Explanation: The NT flag is set by CALL or INT initiated task switch operations.




7 - Question

The 80286 executes LMSW instruction to enter into
a) real addressing mode
b) protected mode
c) real addressing and protected modes
d) none of the mentioned

View Answer

Answer: b
Explanation: To enter into protected mode, 80286 executes LMSW instruction, that sets PE flag.




8 - Question

The instruction that sets the zero flag, if the segment referred to, by the selector can be read is
a) VERW
b) VERR
c) LSL
d) LAR

View Answer

Answer: b
Explanation: The VERR (VERify to Read) instruction sets the zero flag, if the segment referred to, by the selector, can be read.




9 - Question

The instruction that sets the zero flag, if the segment referred to by the selector, can be written as
a) VERW
b) APRL
c) LSL
d) LAR

View Answer

Answer: a
Explanation: The VERW (VERify to Write) instruction sets the zero flag, if the segment referred to, by the selector can be written.




10 - Question

The instruction that reads the descriptor access rights byte into the register is
a) VERW
b) APRL
c) LSL
d) LAR

View Answer

Answer: d
Explanation: The LAR (Load Access Rights) instruction reads the descriptor access rights byte into the register, if privilege rules allow.




11 - Question

The instruction that reads the segment limit into the register, if privilege rules and descriptor type allow is
a) VERW
b) APRL
c) LSL
d) LAR

View Answer
Answer: c
Explanation: The LSL (Load Segment Limit) instruction reads the segment limit into the register, if privilege rules, and descriptor type allow.

 




12 - Question

The instruction that adjusts the RPL (Requested Privilege Level) of the selector, to the numeric maximum of current selector RPL value is
a) LAR
b) VERR
c) LSL
d) APRL

View Answer

Answer: d
Explanation: The APRL (Adjust Requested Privilege Level) adjusts the RPL (Requested Privilege Level) of the selector to the numeric maximum of current selector RPL value, and the RPL value in the register.

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