Computer Architecture Questions Medium
The fetch-decode-execute cycle, also known as the instruction cycle, is the fundamental process that a computer system follows to execute instructions. It consists of three main steps: fetch, decode, and execute.
1. Fetch: In this step, the computer fetches the next instruction from the memory. The program counter (PC) holds the address of the next instruction to be fetched. The PC is incremented to point to the next instruction after the current one is fetched. The fetched instruction is stored in the instruction register (IR).
2. Decode: Once the instruction is fetched, it needs to be decoded to determine the operation to be performed and the operands involved. The control unit interprets the instruction stored in the IR and generates the necessary control signals to execute the instruction.
3. Execute: In this step, the decoded instruction is executed by the appropriate functional units of the computer system. This may involve performing arithmetic or logical operations, accessing memory or I/O devices, or transferring data between registers. The execution of the instruction modifies the state of the computer system, such as updating the values in registers or memory.
After the execution of an instruction, the cycle repeats by fetching the next instruction from memory, and the process continues until the program is complete or interrupted. The fetch-decode-execute cycle is the basic building block of the computer's operation, allowing it to execute a sequence of instructions to perform complex tasks.