The CPU

The central processing unit (CPU), or sometimes simply processor is the brain of any computer system. It’s usually built into a single chip. Every computer chip today is a piece of silicon with billions of transistors that together constitute the central processing unit of a computer.

The CPU is linked to main memory, peripheral equipment (including input/output devices), and storage units. The fundamental operation of most CPUs is to execute a sequence of stored instructions called a program. The CPU receives various types of input and produces specific outputs. The choice of processor decides the speed of computing and its multitasking ability. The majority of processors are capable of carrying out a single instruction at a time. However, the one instruction is executed at lightning speed. The speed of a processor is measured in gigahertz (GHz).

There are three typical parts of the CPU:

· the arithmetic and logic unit (ALU);

· the control unit (CU);

· the registers.

The Arithmetic and Logical Unit, or ALU, is the device that performs elementary operations such as arithmetic operations (addition, subtraction, multiplication, division and so on), logical operations (AND, OR, NOT), and comparison operations (for example, comparing the contents of two "slots" for equality). This unit is where the "real work" is done.

The control unit keeps track of which slot contains the current instruction that the computer is performing, telling the ALU what operation to perform and retrieving the information (from the memory) that it needs to perform it, and transfers the result back to the appropriate memory location.