<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> An instruction cycle (also known as the fetch--decode--execute cycle or the fetch - execute cycle) is the basic operational process of a computer . It is the process by which a computer retrieves a program instruction from its memory, determines what actions the instruction dictates, and carries out those actions . This cycle is repeated continuously by a computer's central processing unit (CPU), from boot - up to when the computer is shut down . </P> <P> In simpler CPUs the instruction cycle is executed sequentially, each instruction being processed before the next one is started . In most modern CPUs the instruction cycles are instead executed concurrently, and often in parallel, through an instruction pipeline: the next instruction starts being processed before the previous instruction has finished, which is possible because the cycle is broken up into separate steps . </P>

What executes the sequencing of instructions in the cpu