<P> A central processing unit (CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input / output (I / O) operations specified by the instructions . The computer industry has used the term "central processing unit" 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 . </P> <P> The form, design, and implementation of CPUs have changed over the course of their history, but their fundamental operation remains almost unchanged . Principal components of a CPU include the arithmetic logic unit (ALU) that performs arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations and a control unit that orchestrates the fetching (from memory) and execution of instructions by directing the coordinated operations of the ALU, registers and other components . </P> <P> Most modern CPUs are microprocessors, meaning they are contained on a single integrated circuit (IC) chip . An IC that contains a CPU may also contain memory, peripheral interfaces, and other components of a computer; such integrated devices are variously called microcontrollers or systems on a chip (SoC). Some computers employ a multi-core processor, which is a single chip containing two or more CPUs called "cores"; in that context, one can speak of such single chips as "sockets". </P>

The core of the processor is composed of the alu and