Understanding the Fetch Decode Execute Cycle

What are the main stages of the fetch cycle?

• Read, Analyze, Compute, Transfer, Finalize

• Fetch, Decode, Execute, Store, Complete

• Load, Process, Save, Retrieve, Finish

• Instruction Fetch, Instruction Decode, Execute, Memory Access, Write Back

Answer explanation

The correct stages of the fetch cycle are Instruction Fetch, Instruction Decode, Execute, Memory Access, and Write Back. These steps describe how a CPU processes instructions in a systematic manner.

Describe the role of the program counter in the fetch cycle.

• The program counter holds the address of the next instruction to be fetched and is incremented after each fetch.

• The program counter manages memory allocation during the fetch cycle.

• The program counter is responsible for executing the current instruction.

• The program counter stores the results of the last instruction executed.

Answer explanation

The program counter is crucial in the fetch cycle as it holds the address of the next instruction to be fetched and increments after each fetch, ensuring the CPU processes instructions in the correct sequence.

What is the purpose of the instruction register during the fetch cycle?

• To execute the fetched instruction immediately.

• To decode the fetched instruction before execution.

• To hold the fetched instruction from memory.

• To store the address of the next instruction to be fetched.

Answer explanation

The instruction register holds the fetched instruction from memory during the fetch cycle, allowing the CPU to later decode and execute it. This is essential for the proper functioning of the instruction execution process.

How does the memory address register function in the fetch cycle?

• The MAR stores the data retrieved from memory during the fetch cycle.

• The MAR holds the results of the last computation performed by the CPU.

• The MAR holds the address of the memory location to fetch data from during the fetch cycle.

• The MAR is responsible for executing instructions in the fetch cycle.

Answer explanation

The correct choice is that the MAR holds the address of the memory location to fetch data from during the fetch cycle. It does not store data or results, nor does it execute instructions.

Explain the process of instruction decoding.

• Instruction decoding is the process of interpreting binary instructions fetched from memory to prepare them for execution.

• Instruction decoding is the process of storing instructions in memory for future use.

• Instruction decoding is the process of converting high-level code into machine language.

• Instruction decoding involves executing the instructions directly without interpretation.

Answer explanation

Instruction decoding involves interpreting binary instructions fetched from memory, allowing the CPU to understand and prepare them for execution. This is essential for the correct operation of programs.

What is the significance of opcode in instruction decoding?

• The opcode indicates the specific operation to be performed during instruction decoding.

• The opcode determines the memory address for data storage.

• The opcode is used to manage CPU power consumption.

• The opcode specifies the data type of the operands.

Answer explanation

The opcode is crucial in instruction decoding as it specifies the exact operation the CPU must perform, guiding the execution of instructions effectively.

How does the control unit contribute to instruction decoding?

• The control unit executes the instruction directly without decoding.

• The control unit decodes the instruction by interpreting the opcode and generating control signals for execution.

• The control unit only manages memory access during instruction execution.

• The control unit generates output signals without interpreting the opcode.

Answer explanation

The control unit decodes instructions by interpreting the opcode, which specifies the operation to be performed, and generates the necessary control signals to execute the instruction, making this choice correct.

What are the key functions of the execution unit?

• Storing data in memory

• The key functions of the execution unit include performing arithmetic and logical operations, managing data flow, and executing instructions.

• Transferring data between devices

• Managing user input and output

Answer explanation

The execution unit is responsible for executing instructions, performing arithmetic and logical operations, and managing data flow, making it essential for processing tasks in a computer.

How does the execution unit interact with the arithmetic logic unit (ALU)?

• The execution unit only retrieves data from the ALU without sending instructions.

• The execution unit interacts with the ALU by sending instructions for arithmetic and logical operations, and receiving the results.

• The ALU directly controls the execution unit's clock speed.

• The execution unit bypasses the ALU for all operations.

Answer explanation

The correct choice explains that the execution unit sends instructions to the ALU for arithmetic and logical operations and receives the results, highlighting the collaborative interaction between these components.

What types of operations can the execution unit perform?

• Input and output operations.

• Data storage and retrieval operations.

• Arithmetic, logical, and comparison operations.

• Memory management operations.

Answer explanation

The execution unit primarily performs arithmetic, logical, and comparison operations, which are essential for processing data and executing instructions in a computer. Other options do not accurately describe its main functions.