The Central Processing Unit, or CPU for short, executes all of the computer's directions. Essentially, the CPU is the brains of the computer. Similar to the human brain, it processes data and calculates solutions. The CPU receives “inputs” - data from commands which come from human users via peripherals or software - and calculates “outputs” - data created by the computer itself. Housed in the Motherboard and generated by the Power Supply, the CPU is a microchip the size of a small square cracker. Generally speaking, it is the most important and necessary component of any modern computer.
The CPU itself has many different subcomponents for the numerous functions it must complete. Arithmetic-logic unit deals with addition, subtraction, multiplication, and division, while determining absolute value. It uses binary form for its number system. The built-in clock, as the name implies, deals with time and timing. More specifically, it deals with the coordination and speed rate of functions. The “control unit” of the CPU can perform four major operations: fetch (retrieving instructions from memory) , decode (“reading” the fetch function), execute (carrying out the function), and write-back (displaying the product of the completed function). On some computers, the memory management unit is a component of the CPU.
CPU’s vary in their abilities and instruction sets - the program instructions. There are two major models; the Complex Instruction Set Computer, or CISC, and the Reduced Instruction Set, or RISC. CISC attempts to complete a task as simply as possible. Therefore the software and human interaction is very limited and simple, however this method is computationally more intense which has a negative impact on battery life. RISC, on the other hand, uses a more complex software and requires compiler work. It competes tasks at quicker rate while using less battery life. Today most CPUs are in RISC form.