Describe the process of instruction fetching and decoding in a CPU.

The process of instruction fetching and decoding in a CPU involves several steps.

1. Fetching:
During the fetching stage, the CPU retrieves the next instruction from the memory. The program counter (PC) holds the address of the next instruction to be fetched. The CPU sends this address to the memory unit, which then retrieves the instruction from the specified memory location and sends it back to the CPU.

2. Instruction Register (IR):
Once the instruction is fetched, it is stored in a special register called the Instruction Register (IR). The IR holds the binary representation of the instruction, which includes the opcode (operation code) and any associated operands or addressing modes.

3. Decoding:
After the instruction is stored in the IR, the CPU proceeds to decode it. The decoding stage involves interpreting the opcode and determining the specific operation that needs to be performed. The CPU uses the opcode to identify the appropriate control signals and data paths required for executing the instruction.

4. Operand Fetching:
If the instruction requires any operands, the CPU fetches them from the memory or registers based on the addressing mode specified in the instruction. The operands may be fetched from memory locations or from specific registers within the CPU.

5. Execution:
Once the instruction is fetched, decoded, and the operands are fetched, the CPU proceeds to execute the instruction. The execution stage involves performing the actual operation specified by the opcode, such as arithmetic calculations, logical operations, or data transfers.

6. Incrementing the Program Counter:
After the instruction is executed, the program counter (PC) is incremented to point to the next instruction in memory. This prepares the CPU for the next fetch and decode cycle, allowing it to continue executing the program sequentially.

Overall, the process of instruction fetching and decoding in a CPU involves fetching the instruction from memory, storing it in the instruction register, decoding the opcode, fetching any required operands, executing the instruction, and incrementing the program counter to prepare for the next instruction. This cycle repeats until the program is completed.