What is Instruction Cycle

A program residing in the memory unit of the computer having of a sequence of instructions.  The program is implemented in the computer by going through a cycle for each instruction.  Every instruction cycle in turn is subdivided into a sequence of sub cycles or phases.  In the basic computer each instruction cycle having of the following phases:

 1. Fetch an instruction from memory.

 2. Decode the instruction

 3. Read the effective address from memory if the instruction has an indirect address.

 4. Execute the instruction.