The function of the CPU (Centeral Processing Unit) is to perform operations which make your computer run. A CPU is the brain of a computer, according to About.com's Tim Fisher. A central processing unit (CPU), also called a central processor or main processor, is the electronic circuitry within a computer that executes instructions that make up a computer program.The CPU performs basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions in the program. This is why the CPU is known as the "brain" of the PC.
The rest of the computer is just there to enable the CPU to communicate with other things (other computers / humans / printers / scanners / etc. Short for "central processing unit," the CPU interprets commands before executing them. A CPU uses complex algorithms and programming to interpret signals and code.
Every operation that is carried out, including key strokes, opening and closing programs, and saving files, is carried out by the CPU. That’s actually where all the real work happens. The main function of the CPU is processing instructions given to the computer. The CPU is also called a processor or central processor.