Flags and Status Registers MCQs

By: Prof. Dr. Fazal Rehman Shamil | Last updated: September 20, 2024

1. What is the primary purpose of the status register in a microprocessor?

a) To control the clock speed
b) To store data temporarily
c) To indicate the state of the processor
d) To manage memory operations

Answer: c) To indicate the state of the processor


2. Which flag is set when the result of an arithmetic operation is zero?

a) Carry Flag
b) Zero Flag
c) Sign Flag
d) Parity Flag

Answer: b) Zero Flag


3. The Carry Flag (CF) is set when a(n) ______ occurs during an arithmetic operation.

a) Overflow
b) Underflow
c) Borrow or carry
d) Shift

Answer: c) Borrow or carry


4. What is the function of the Parity Flag (PF)?

a) Indicates if a result is positive or negative
b) Checks if an overflow occurred
c) Determines the parity of the result (even or odd)
d) Indicates if a division by zero occurred

Answer: c) Determines the parity of the result (even or odd)


5. Which flag is used to indicate whether a subtraction resulted in a borrow?

a) Carry Flag
b) Overflow Flag
c) Zero Flag
d) Sign Flag

Answer: a) Carry Flag


6. What does the Overflow Flag (OF) indicate?

a) An arithmetic result exceeds the capacity of the destination operand
b) A logical error in the program
c) Memory overflow
d) A division by zero error

Answer: a) An arithmetic result exceeds the capacity of the destination operand


7. When the result of an operation is negative, which flag is set?

a) Sign Flag
b) Zero Flag
c) Carry Flag
d) Overflow Flag

Answer: a) Sign Flag


8. The Auxiliary Carry Flag (AF) is mainly used for which type of arithmetic operation?

a) Floating-point
b) Addition
c) Binary-coded decimal (BCD)
d) Multiplication

Answer: c) Binary-coded decimal (BCD)


9. The Zero Flag (ZF) is cleared when the result of an arithmetic operation is:

a) Non-zero
b) Negative
c) Positive
d) Overflow

Answer: a) Non-zero


10. What is the size of the flags register in most x86 processors?

a) 8 bits
b) 16 bits
c) 32 bits
d) 64 bits

Answer: b) 16 bits


11. Which of the following flags is NOT a part of the condition code register (CCR)?

a) Overflow Flag
b) Zero Flag
c) Parity Flag
d) Stack Pointer Flag

Answer: d) Stack Pointer Flag


12. In a microcontroller, which flag is commonly set when a subtraction results in a borrow?

a) Carry Flag
b) Overflow Flag
c) Zero Flag
d) Auxiliary Flag

Answer: a) Carry Flag


13. The Sign Flag is set if the result of an operation is:

a) Positive
b) Even
c) Negative
d) Zero

Answer: c) Negative


14. In which scenario is the Carry Flag set to 1?

a) When an arithmetic operation results in overflow
b) When an arithmetic operation causes a borrow or carry
c) When an operand exceeds the memory limit
d) When a division results in a non-integer value

Answer: b) When an arithmetic operation causes a borrow or carry


15. The purpose of the Direction Flag (DF) in x86 processors is to:

a) Control data transfer direction in string instructions
b) Indicate the result of division
c) Store the program counter
d) Control interrupts

Answer: a) Control data transfer direction in string instructions


16. What does the Interrupt Flag (IF) control in a processor?

a) Execution of arithmetic instructions
b) Enabling and disabling of interrupts
c) Direction of memory access
d) Status of peripheral devices

Answer: b) Enabling and disabling of interrupts


17. Which flag is cleared to prevent interrupts in a microprocessor?

a) Zero Flag
b) Overflow Flag
c) Interrupt Flag
d) Direction Flag

Answer: c) Interrupt Flag


18. The Overflow Flag (OF) is set during which of the following conditions?

a) Division by zero
b) Memory read failure
c) When signed overflow occurs in arithmetic operations
d) When even parity is detected

Answer: c) When signed overflow occurs in arithmetic operations


19. When a processor encounters an even number of 1’s in a result, the Parity Flag is:

a) Set to 1
b) Cleared to 0
c) Ignored
d) Inverted

Answer: a) Set to 1


20. What does the Auxiliary Carry Flag (AF) indicate?

a) A carry from bit 3 to bit 4 in a binary addition
b) A borrow during subtraction
c) A sign change in the result
d) Overflow in multiplication

Answer: a) A carry from bit 3 to bit 4 in a binary addition


21. Which flag is used to detect errors in transmission systems?

a) Zero Flag
b) Carry Flag
c) Parity Flag
d) Sign Flag

Answer: c) Parity Flag


22. The Direction Flag (DF) is cleared to make string operations process:

a) Left to right
b) Right to left
c) Bottom to top
d) Random order

Answer: a) Left to right


23. Which register contains flags like Zero, Carry, and Overflow in most processors?

a) Data Register
b) Instruction Register
c) Status Register
d) Memory Address Register

Answer: c) Status Register


24. When the result of an addition overflows a signed integer’s range, which flag is set?

a) Overflow Flag
b) Carry Flag
c) Zero Flag
d) Sign Flag

Answer: a) Overflow Flag


25. Which flag can indicate that no more instructions should be executed in a pipeline?

a) Zero Flag
b) Halt Flag
c) Interrupt Flag
d) Direction Flag

Answer: b) Halt Flag


26. In a microprocessor, which flag is checked to determine if a loop operation should continue?

a) Sign Flag
b) Carry Flag
c) Zero Flag
d) Overflow Flag

Answer: c) Zero Flag


27. When the result of an arithmetic operation is even, which flag will be set?

a) Sign Flag
b) Zero Flag
c) Parity Flag
d) Carry Flag

Answer: c) Parity Flag


28. Which of the following flags will be cleared if the result of an operation is positive?

a) Zero Flag
b) Carry Flag
c) Sign Flag
d) Overflow Flag

Answer: c) Sign Flag


29. The Zero Flag is primarily used to:

a) Indicate a non-zero result
b) Indicate that a division was performed
c) Check for an overflow error
d) Indicate whether the result of an operation is zero

Answer: d) Indicate whether the result of an operation is zero


30. Which flag is used to signal when an arithmetic result is too large for the destination operand?

a) Carry Flag
b) Zero Flag
c) Overflow Flag
d) Sign Flag

Answer: c) Overflow Flag


31. The Direction Flag (DF) is typically used in which type of instruction?

a) Arithmetic
b) Logical
c) String
d) Branch

Answer: c) String


32. Which flag is often checked before branching in conditional jump instructions?

a) Parity Flag
b) Sign Flag
c) Carry Flag
d) Zero Flag

Answer: d) Zero Flag


33. In x86 architecture, which flag is set if the result is less than zero in a subtraction operation?

a) Carry Flag
b) Sign Flag
c) Zero Flag
d) Overflow Flag

Answer: b) Sign Flag


34. What is the main function of the Status Register in most CPUs?

a) To store memory addresses
b) To manage hardware interrupts
c) To reflect the result of the last operation
d) To indicate the power status

Answer: c) To reflect the result of the last operation


35. Which of the following flags is used in decimal arithmetic operations?

a) Sign Flag
b) Auxiliary Carry Flag
c) Overflow Flag
d) Direction Flag

Answer: b) Auxiliary Carry Flag


36. The Carry Flag (CF) is typically checked in which of the following operations?

a) Branching
b) Addition and subtraction
c) Multiplication
d) Memory access

Answer: b) Addition and subtraction


37. When the Zero Flag (ZF) is set, it usually indicates:

a) An overflow occurred
b) The result was negative
c) The result was zero
d) The operation was not performed

Answer: c) The result was zero


38. What happens to the Overflow Flag if an addition operation exceeds the signed integer limit?

a) It is set to 1
b) It is cleared to 0
c) It causes a system interrupt
d) It resets the CPU

Answer: a) It is set to 1


39. The Parity Flag is used to check:

a) Whether an instruction is valid
b) The parity (even or odd) of the number of 1’s in the result
c) The overflow of a result
d) The size of the operand

Answer: b) The parity (even or odd) of the number of 1’s in the result


40. Which flag indicates that a string operation will proceed from lower to higher memory addresses?

a) Sign Flag
b) Direction Flag (DF)
c) Carry Flag
d) Overflow Flag

Answer: b) Direction Flag (DF)


41. When a microprocessor executes a logical AND operation, which flag is NOT affected?

a) Zero Flag
b) Sign Flag
c) Carry Flag
d) Parity Flag

Answer: c) Carry Flag


42. Which flag is typically affected by an arithmetic right shift operation?

a) Zero Flag
b) Sign Flag
c) Parity Flag
d) Carry Flag

Answer: d) Carry Flag


43. In an x86 processor, the condition of which flag is used to control the IN/OUT instructions?

a) Direction Flag
b) Interrupt Flag
c) Carry Flag
d) Overflow Flag

Answer: b) Interrupt Flag


44. Which flag can help identify if the system has encountered an integer overflow error?

a) Zero Flag
b) Overflow Flag
c) Parity Flag
d) Carry Flag

Answer: b) Overflow Flag


45. In a string comparison, which flag is crucial in determining if the strings are equal?

a) Carry Flag
b) Zero Flag
c) Overflow Flag
d) Sign Flag

Answer: b) Zero Flag


46. What does it mean when the Carry Flag is set to 1 after a subtraction?

a) The result is negative
b) The result is zero
c) There was a borrow in the operation
d) An overflow occurred

Answer: c) There was a borrow in the operation


47. The Auxiliary Carry Flag is set during operations that involve:

a) Even number of 1’s
b) Binary-coded decimal arithmetic
c) Unsigned overflow
d) Floating-point operations

Answer: b) Binary-coded decimal arithmetic


48. The direction of string operations in assembly language is controlled by the:

a) Sign Flag
b) Overflow Flag
c) Direction Flag
d) Interrupt Flag

Answer: c) Direction Flag


49. Which flag is used in signed number arithmetic to indicate a change in sign?

a) Sign Flag
b) Carry Flag
c) Parity Flag
d) Auxiliary Carry Flag

Answer: a) Sign Flag


50. If the result of a computation is zero, which flag will be set to 1?

a) Overflow Flag
b) Carry Flag
c) Zero Flag
d) Sign Flag

Answer: c) Zero Flag

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