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Machine cycle

Machine cycle

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:

  1. 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.
  2. Decode. The CPU decodes the instructions to determine what operation needs to be performed and what data is required.
  3. Execute. Instructions are executed with results stored in memory or in a register.
  4. Store. The CPU stores any results or changes to memory that were made during the execution of the instruction.
  5. 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.

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