The instruction cycle is the basic operation cycle of computers, and it is the time period during which the computer fetches an instruction and executes it. It consists of up to six phases, which are fetch instruction, decode instruction, evaluate address, fetch operand, execute and store results.
This cycle is repeated continuously from the time a computer boots up to the time it is shut down. Simple computers execute these cycles in a series, while most modern computers do many cycles simultaneously. Instruction cycle refers to both the series of steps and the time it takes to execute those steps. The fetch instruction and decode are the same for all instruction cycles.