CPU

The main unit inside the computer is CPU. CPU stands for ' Central Processing Unit ' and it is the brain of computer. Without CPU there is nothing. This unit is responsible for all events inside the computer. It controls every internal and external devices, performs arithmetic and logic operations. The CPU consists of electronic circuits that interpret and execute instructions; it communicates with the input, output, and storage devices. The CPU with the help of memory executes instructions in the repetition of machine cycles. Most CPU's today are made by Intel and bear such names as ' Pentium Pro', ' Pentium II '. 'Pentium III ' and ' Pentium 4 '. Older Intel CPU's include the 80486 and 80386 families. Other Manufacturers also make CPU's: Motorola for Macintosh, AMD and Cirrus for PC's and others. The Speed of a CPU's is measured in megahertz.

The CPU is composed of main two units

The Control Unit (CU)

Directs and controls the activities of the internal and external devices. It interprets the instructions obtained into the computer, determines what data are needed, where it is stored, where  to store the results of the operation, and sends the control signals to the devices involved in the execution of instructions.

The Arithmetic and Logic Unit (ALU)

 Is the part where actual computations take place. It consists of circuits, which perform arithmetic operations (e.g. addition, subtraction, multiplication, division) over data received from memory and capable to compare numbers.