A small wafer-thin chip with lots of pins on one side of it. The CPU is actually an integrated circuit containing millions of transistors. CPU, Microprocessor, Processor or whatever name you decide to give it, is where all the action begins. Its function is to execute programs stored in the main memory by fetching their instructions, examining them, and then executing them one after another. One must think in terms of human anatomy, it is essentially the brain of your computer. Just like the brain controls your body, the CPU essentially controls and directs all the functions of your computer.