MCQ On Control Unit
Q1. The Control unit of a computer _______.
- Stores data in the memory
- Accepts input data from the keyboard
- generates control signals to execute an instruction
- none of the above
Answer: c, generates control signals to execute an instruction
Solution: Generates control signals to coordinate how data moves between memory, the ALU, and input/output devices.
Q2. Basic task for control unit is.
- Sequencing
- execution
- both a & b
- none of the above
Answer: c, both a & b
Q3. Generation of appropriate control signals to execute a series of micro operations in proper sequence is done by.
- Sequencing
- execution
- ALU
- CPU
Answer: a, Sequencing
Solution: The Control Unit (CU) is responsible for ensuring that all micro-operations inside the CPU occur in the proper order. This is achieved through its sequencing function, which generates the appropriate control signals step by step.
Q4. Execution task of control unit is responsible for.
- Executing micro program
- Executing an instruction
- Executing micro operation
- Executing each micro operation
Answer: d, Executing each micro operation
Solution: The Control Unit (CU) breaks every machine instruction into very small steps called micro-operations (for example: transfer data from register to ALU, increment program counter, etc.).
Q5. Hardwired control unit is implemented as.
- Sequential logic
- finite state machine
- both a & b
- none of the above
Answer: c, both a & b
Solution: A hardwired control unit is built entirely with electronic circuits (gates, flip-flops, decoders, etc.) rather than using microprograms. It behaves as: Sequential logic – because it uses flip-flops and timing signals to step through a sequence of control states. Finite State Machine (FSM) – because each control step is a defined state, and the unit moves from one state to another based on the instruction and current state. Thus a hardwired control unit is implemented as sequential logic and a finite state machine.
Q6. Which of the following statements correctly compares Hardwired and Micro-programmed control units?.
- Hardwired control is slower but easier to modify than micro-programmed.
- Hardwired control is faster but difficult to modify.
- Micro-programmed control is faster and more complex.
- Both have same speed and flexibility.
Answer: b, Hardwired control is faster but difficult to modify.
Solution: Hardwired uses fixed logic circuits (fast) but any change needs hardware redesign.
Q7. A micro-programmed control unit stores the control information in:.
- Cache memory
- Control memory (ROM or Control Store)
- RAM used for instructions
- CPU registers only
Answer: b, Control memory (ROM or Control Store)
Solution: Microinstructions are stored in a control memory or control store.
Q8. Which one is not an advantage of micro-programmed control?.
- Easier to implement complex instructions
- Easy to modify and update
- Higher operating speed than hardwired control
- Simplifies design of control logic
Answer: c, Higher operating speed than hardwired control
Solution: Micro-programmed is typically slower than hardwired.
Q9. In a hardwired control unit, control signals are generated by:.
- Software routines
- Combinational logic circuits and sequential circuits
- Control store microinstructions
- I/O processors
Answer: b, Combinational logic circuits and sequential circuits
Solution: Hardwired control uses combinational and sequential logic to produce control signals.
Q10. Which one is true for a micro-programmed control unit?.
- Control signals are generated using finite-state logic only
- Control signals are generated by reading microinstructions
- No memory is involved
- It cannot implement complex instruction sets
Answer: b, Control signals are generated by reading microinstructions
Solution: Control signals are generated by fetching and decoding microinstructions.
Q11. The control memory used in micro-programmed control unit is generally implemented using:.
- Magnetic tape
- Semiconductor ROM or PLA
- Cache SRAM
- DRAM main memory
Answer: b, Semiconductor ROM or PLA
Solution: Control memory is typically ROM or PLA.
Q12. Which of these statements is correct about micro-programmed control?.
- Only suitable for RISC processors
- Used in many CISC processors like early Intel CPUs
- Requires hardware change for every new instruction
- Cannot be pipelined
Answer: b, Used in many CISC processors like early Intel CPUs
Solution: CISC processors commonly use micro-programmed control.
Q13. If flexibility and ease of modification are more important than speed, the preferred control unit is:.
- Hardwired control
- Micro-programmed control
- Either A or B
- None of the above
Answer: b, Micro-programmed control
Solution: Micro-programmed control is easier to modify and extend than hardwired control.
Q14. Which of the following processors generally uses hardwired control?.
- Complex Instruction Set Computers (CISC)
- Reduced Instruction Set Computers (RISC)
- Both RISC and CISC
- None
Answer: b, Reduced Instruction Set Computers (RISC)
Solution: RISC processors need very high speed and simple instructions which suits hardwired design.
Q15. What is a microinstruction?.
- A high-level machine language command
- A single control word stored in control memory that generates control signals
- An assembly instruction
- A single clock pulse
Answer: b, A single control word stored in control memory that generates control signals
Solution: A microinstruction is a control word stored in control memory to generate control signals.
Q16. in micro programmed control unit, micro instructions are stored in special memory called.
- control memory
- RAM
- ROM
- micro memory
Answer: a, control memory
Solution: in a micro-programmed control unit, micro-instructions are stored in special memory called control memory.
Q17. Hardwired control unit uses ____to interpret an instruction.
- Special Program
- Special micro
- fixed logic
- instruction register
Answer: c, fixed logic
Solution: a hardwired control unit uses fixed logic circuits to interpret an instruction.
Q18. While designing hardwired control unit factor to be considered.
- amount of hardware used
- Speed of operation
- cost of design
- all of the above
Answer: d, all of the above
Solution: amount of hardware used, speed of operation, and cost of design are all key factors when designing a hardwired control unit.
Q19. state table method is the method for designing.
- Hardwired control unit
- micro programme d contro
- both a & b
- none of the above
Answer: a, Hardwired control unit
Solution: the state table method is used for designing a hardwired control unit.
Q20. In state table method it minimize the amount of.
- software
- hardware
- both a & b
- none of the above
Answer: c, both a & b
Solution: The state table method is used in digital system and sequential circuit design (e.g., designing finite state machines).
Q21. Microprogram consisting of _______ is stored in control memory of control unit.
- instructions
- micro instructions
- micro program
- macro program
Answer: b, micro instructions
Solution: In a microprogrammed control unit, the control memory stores a microprogram. This microprogram is made up of microinstructions, and each microinstruction specifies the control signals (like register transfer, ALU operation, memory read/write, etc.) required for one step of executing a machine instruction.
Q22. control signals are generated by execution of.
- instructions
- micro instructions
- micro program
- macro program
Answer: b, micro instructions
Solution: control signals are produced when microinstructions are executed.
Q23. A sequence of micro instructions is called.
- instructions
- micro instructions
- micro program
- macro program
Answer: c, micro program
Solution: Microprogram = sequence of microinstructions
Q24. A micro instruction can causeexecution of one or more.
- micro instructions
- micro program
- macro program
- micro operations
Answer: d, micro operations
Solution: A microinstruction is the smallest control step in a microprogrammed control unit. Each microinstruction specifies the control signals needed to perform one or more micro-operations (such as moving data between registers, performing an ALU operation, reading/writing memory, etc.) during a single clock cycle.
Q25. A micro instruction consists of.
- oneor more micro operation to be executed
- address of next micro operation to be executed
- oneor more macro operation to be executed
- both a & b
Answer: d, both a & b
Q26. Micro instructions are divided into.
- Horizontal
- vertical
- both a & b
- none of the above
Answer: c, both a & b
Q27. Input to control unit.
- IR
- ALU flags
- Clock
- all of the above
Answer: d, all of the above
Solution: The control unit (CU) receives several types of input signals so it can generate the correct control signals for the CPU
Q28. delay element method used to design.
- Hardwired control unit
- micro programmed control
- both a & b
- none of the above
Answer: a, Hardwired control unit
Q29. A micro instruction has ____.
- Control field
- address field
- both a & b
- none of the above
Answer: c, both a & b
Q30. Micro programming can be used for high level language support.
- TRUE
- FALSE
Answer: a, TRUE
Solution: Microprogramming can be designed to directly support high-level language features.
Q31. Microprogramming can be used for.
- Emulation
- Operating system support
- realization of special purpose devices
- all of the above
Answer: d, all of the above