Q.1 Which of the following best defines a micro-operation in a CPU?
A high-level programming instruction
A basic operation performed on the data stored in registers
An operation performed by the ALU only
A memory access instruction
Explanation - Micro-operations are elementary operations performed on the data stored in the registers of a CPU, such as shifting, incrementing, or transferring data.
Correct answer is: A basic operation performed on the data stored in registers
Q.2 Which of the following is a type of micro-operation?
Arithmetic
Logical
Shift
All of the above
Explanation - Micro-operations can be arithmetic (add, subtract), logical (AND, OR), or shift operations (left shift, right shift).
Correct answer is: All of the above
Q.3 Which register temporarily holds data being transferred from memory to another register?
Program Counter
Memory Buffer Register
Instruction Register
Accumulator
Explanation - The Memory Buffer Register (MBR) temporarily holds data coming from memory before it is transferred to another register.
Correct answer is: Memory Buffer Register
Q.4 The control unit in a CPU is responsible for:
Executing arithmetic operations
Generating control signals to direct micro-operations
Storing data
Performing logical operations
Explanation - The control unit generates signals that direct the operation of the CPU, controlling the sequence of micro-operations.
Correct answer is: Generating control signals to direct micro-operations
Q.5 Which of the following is NOT a function of the control unit?
Fetching instructions
Decoding instructions
Executing instructions directly
Generating timing and control signals
Explanation - The control unit directs other units to execute instructions; it does not execute instructions itself.
Correct answer is: Executing instructions directly
Q.6 A shift micro-operation can be used for:
Multiplication by powers of two
Division by powers of two
Data serialization
All of the above
Explanation - Shift operations can be used to multiply/divide by powers of two and to serialize data in registers.
Correct answer is: All of the above
Q.7 Which of the following statements about a register transfer language (RTL) is true?
It is used to describe instruction set architecture
It describes data flow between registers and memory at micro-operation level
It is a type of high-level programming language
It is used for network communication protocols
Explanation - RTL is used to express the operations of a CPU at the micro-operation level, showing transfers of data between registers and memory.
Correct answer is: It describes data flow between registers and memory at micro-operation level
Q.8 Which register holds the address of the next instruction to be executed?
Program Counter (PC)
Instruction Register (IR)
Memory Address Register (MAR)
Accumulator (AC)
Explanation - The Program Counter (PC) holds the address of the next instruction to be fetched from memory.
Correct answer is: Program Counter (PC)
Q.9 A microinstruction that activates multiple control signals simultaneously is called:
Horizontal microinstruction
Vertical microinstruction
Sequential microinstruction
Branch microinstruction
Explanation - Horizontal microinstructions can activate multiple control signals in parallel, allowing several micro-operations to occur simultaneously.
Correct answer is: Horizontal microinstruction
Q.10 The main purpose of the instruction register (IR) is:
To store data from memory temporarily
To hold the currently executing instruction
To perform arithmetic operations
To point to the next instruction
Explanation - The IR holds the instruction that is currently being executed, allowing the control unit to decode it and generate appropriate control signals.
Correct answer is: To hold the currently executing instruction
Q.11 Which type of micro-operations involve only logical operations like AND, OR, and NOT?
Arithmetic micro-operations
Shift micro-operations
Logical micro-operations
Control micro-operations
Explanation - Logical micro-operations operate on binary data within registers using logical operations such as AND, OR, and NOT.
Correct answer is: Logical micro-operations
Q.12 Which of the following is true for a vertical microinstruction?
It activates multiple control signals simultaneously
It uses compact encoding for control signals
It can directly execute arithmetic operations
It stores the contents of registers
Explanation - Vertical microinstructions encode control signals compactly, usually activating one micro-operation per instruction.
Correct answer is: It uses compact encoding for control signals
Q.13 In a CPU, the accumulator (AC) is primarily used for:
Holding memory addresses
Temporary storage during arithmetic and logic operations
Storing instructions
Counting program steps
Explanation - The accumulator is a register used to store intermediate results of arithmetic and logic operations.
Correct answer is: Temporary storage during arithmetic and logic operations
Q.14 Which type of control can be implemented by a sequence counter in a control unit?
Hardwired control
Microprogrammed control
Both hardwired and microprogrammed
None of the above
Explanation - In microprogrammed control, a sequence counter is used to step through microinstructions stored in control memory.
Correct answer is: Microprogrammed control
Q.15 Which of the following is an example of a register transfer?
AC <- AC + DR
PC <- PC + 1
MAR <- Address
All of the above
Explanation - All these statements represent data being transferred between registers or between a register and a functional unit, which is a register transfer.
Correct answer is: All of the above
Q.16 A micro-operation that exchanges the contents of two registers is called:
Shift operation
Swap operation
Clear operation
Complement operation
Explanation - Swap operations exchange the contents of two registers without affecting other registers.
Correct answer is: Swap operation
Q.17 The term 'timing signal' in CPU control refers to:
Signals generated to indicate instruction fetch completion
Signals used to synchronize micro-operations
Signals to select memory addresses
Signals for branching
Explanation - Timing signals coordinate the execution of micro-operations in a CPU, ensuring that operations happen in the correct sequence.
Correct answer is: Signals used to synchronize micro-operations
Q.18 Which of the following is a disadvantage of hardwired control?
High speed
Flexibility is limited
Simple design for small instruction sets
Immediate signal generation
Explanation - Hardwired control is fast but not flexible; changing the instruction set requires redesigning the control circuitry.
Correct answer is: Flexibility is limited
Q.19 Which micro-operation type is involved when the contents of a register are shifted left or right?
Arithmetic micro-operation
Logical micro-operation
Shift micro-operation
Control micro-operation
Explanation - Shift micro-operations move the bits of a register left or right, often used for multiplication or division by powers of two.
Correct answer is: Shift micro-operation
Q.20 A branch microinstruction in microprogramming is used to:
Execute arithmetic operations
Jump to a specified microinstruction address
Load data into registers
Generate timing signals
Explanation - Branch microinstructions change the sequence of microinstructions, allowing conditional or unconditional jumps in microprogram control.
Correct answer is: Jump to a specified microinstruction address
Q.21 The memory address register (MAR) is used for:
Storing the data read from memory
Storing the address of memory location to read/write
Holding instructions being executed
Temporary arithmetic storage
Explanation - MAR holds the memory address from which data is to be read or to which data is to be written.
Correct answer is: Storing the address of memory location to read/write
Q.22 Microprogrammed control differs from hardwired control in that:
It uses fixed logic circuits
It stores control signals in memory
It cannot implement conditional operations
It is faster than hardwired control
Explanation - Microprogrammed control stores sequences of microinstructions in control memory, offering flexibility to modify control logic without changing hardware.
Correct answer is: It stores control signals in memory
Q.23 Which type of micro-operation can set a register to zero?
Clear micro-operation
Shift micro-operation
Swap micro-operation
Complement micro-operation
Explanation - Clear micro-operations set all bits of a register to zero.
Correct answer is: Clear micro-operation
Q.24 The sequence counter in a microprogrammed control unit:
Stores the instruction being executed
Keeps track of the next microinstruction address
Performs arithmetic operations
Controls the program counter
Explanation - The sequence counter helps in stepping through microinstructions sequentially in microprogrammed control units.
Correct answer is: Keeps track of the next microinstruction address