Program counter: A program counter is an integral portion of a computer's Central Processing Unit. It includes a reference to the memory address of the subsequent instruction to be fetched, ready to be executed throughout the next fetch-execute cycle. Instantly obeying an instruction fetch, and the program counter is moved on to refer to the later instruction, before the present instruction is performed. The normal sequential execution of a sequence of instructions might be changed by executing a branch instruction that stores a novel instruction address into the program counter.