Machine Cycle
Definition of Machine cycle A machine cycle, also called a processor cycle or a instruction cycle, is the basic operation performed by a central processing unit (CPU). A CPU is the main logic unit of a computer. A machine cycle consists of a sequence of three steps that is performed continuously and at a rate of millions per second while a computer is in operation. They are fetch, decode and execute. There also is a fourth step, store, in which input and output from the other three phases is stored in memory for later use; however, no actual processing is performed during this step. Fetch step In the fetch step, the control unit requests that main memory provide it with the instruction that is stored at the address (i.e., location in memory) indicated by the control unit's program counter. The control unit is a part of the CPU that also decodes the instruction in the instruction register. A register is a very small amount of very fast memory that is built into th...