A CPU, or Central Processing Unit, is the hardware within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic controlling input/output devices, and managing memory. CPUs are sometimes called microprocessors because they are usually packaged in an integrated circuit called a microprocessor. Early CPUs were often constructed from discrete logic elements with no internal storage; however, modern CPUs typically contain several cache memories and registers, improving performance by reducing the need to access main memory every time data is required.

The term CPU generally refers to a processor chip, which can be one die (chip) in a multi-chip package or one chip in what is now known as an SoC (System on Chip). A multi-core processor contains two or more processors (called “cores”), each of which reads and executes program instructions independently of others—although some architectures allow for communication between cores. The term CPU may also refer collectively to all cores in a multi-core processor.