Components of a Computer System

                  By considering the functions performed by various components, a computer can be represented as a collection of logical components as in Figure 1.3. The main hardware components of a modern computer system are the central processing unit (CPU), the main memory, the secondary storage and the In put-Out put devices.

System Unit

                  The system unit, or the cabinet houses most of the essential components of the computer system such as the power supply, the motherboard, the CPU chip, specialized chips, the system clock, RAM, ROM, expansion board and bus lines.

Central Processing Unit (CPU)

The central processing unit performs the majority of calculations and controls the operation of a computer. CPUs are rated by the speed at which they can execute instructions. The speed of a CPU is measured in Megahertz (MHz), and is also known as the clock speed. The higher the value of the speed the faster the computer can run programs. The capacity of a Central Processing Unit is expressed in terms of word size. A word is the maximum number of bits that the CPU can manipulate or store at one time.

The CPU consists of two parts: the control unit (CU) and the arithmetic/logic unit (ALU)

Different manufactures are making CPUs today. Some of these popular CPUs available today are the Intel, AMD, Cyrix and Motorola.

Control Unit (CU)

                  The control unit controls and directs the operation of the entire computer system. Although it does perform any actual processing on the data, the control unit acts as a central nervous system for the other components of the computer. It obtains instructions from the program stored in main memory, interprets the instructions, and issues signals, which cause other units in the system to execute them.

Arithmetic-Logic Unit (ALU)

                  The arithmetic-Logic unit performs arithmetic operations such as addition, subtraction, multiplication and division on data. It also performs logical operations, which involve comparison of data. In microcomputers, the entire CPU is typically fabricated on a single chip.


                  The motherboard is the main circuit board inside the computer. It can be considered as the main communication center through which all the components of the computer transmit data back and forth. All the main parts including the central processing unit of the computer are typically plugged in to the mother board. The mother board also provides sockets, called expansion slots, to plug in special electronic circuitboards to enhance the functionality of the computer. These extra circuitboards are called expansion cards, by using which you can customize a computer to suit your needs. One other major function of the mother board is to supply the necessary power to all its expansion cards.


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