 In the simplest style of computer architecture, the instruction cycle is very rigid, and runs exactly as specified by the programmer.In the instruction fetch part of the cycle,
the value of the instruction pointer (IP) register is the address of the next instruction to be fetched.This value is placed on the address bus and sent to the memory unit; the memory unit returns the instruction at that address, and it is latched into the instruction register (IR); and the value of the IP is incremented or over-written by a new value (in the case of a jump or branch instruction), ready for the next instruction cycle.