A CPU, also known as a microprocessor, the central processing unit or simply processor, is an electronic circuit that executes commands comprising an instruction, which generates results, within an electronic system. The CPU performs logical, arithmetic, logical, control and output (I/O) operations defined by the instruction written to the microprocessor. Instructions executed by the microprocessor are translated into actual hardware actions through the CPU's instruction bus. The term microprocessor is also used to refer to single or multi-processor computer systems.