A central processing unit (CPU) is the

electronic circuitry

within a


that carries out the


of a

computer program

by performing the basic arithmetic, logical, control and


(I/O) operations specified by the instructions. The term has been used in the computer industry at least since the early 1960s. Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and

control unit

(CU), distinguishing these core elements of a computer from external components such as

main memory

and I/O circuitry