Machine cycle definition
Machine cycle refers to a sequence of steps that a computer’s central processing unit (CPU) goes through in order to execute a single machine language instruction. It is also known as the instruction cycle.
See also: information processing
Steps of a machine cycle:
- Fetch. The CPU must fetch the instructions from the memory location indicated by the program counter, a register that keeps track of the memory address of the next instruction to be executed.
- Decode. The CPU decodes the instructions to determine what operation needs to be performed and what data is required.
- Execute. Instructions are executed with results stored in memory or in a register.
- Store. The CPU stores any results or changes to memory that were made during the execution of the instruction.
- Counter update. Once the machine cycle is complete, the program counter is updated to point to the next instruction to be executed.
Examples of machine cycle:
- Simple processor. Processor used in a calculator might fetch an instruction to add two numbers, decode the instruction to determine the numbers to add, and then execute the addition and display the result.
- Basic processor. Processor used in a simple computer might fetch an instruction, decode it to determine the memory address to load from, execute the load, and store the value in a register.
- Complex processor. A processor used in a modern computer might fetch an instruction, decode it, execute it, and then perform additional steps such as fetching data from cache or memory, performing pipelining, or handling interrupts.