The parts of a computer system

In order to use computers effectively to solve problems in our environment, computer systems are devised. Computer system may be discussed in two parts.

The first part is hardware – the physical, electronic, and electro-mechanical devices that are thought of and recognized as “computers”. The hardware consists of Central Processing Unit (CPU), input devices and output devices. The CPU is made up of a processor and a main memory or main store. The processor carries out, or executes, instructions in the program. The main memory stores input data and the program needed by the processor. The main memory also holds output data, or the results of processing.

Input devices are used to provide data for the CPU. The keyboard is a common data input device. By using a keyboard, a user can enter data directly into the computer system. Data is sometimes entered on cards. The cards are read by an input device called a card reader. Data is often input from a mass storage device, such as magnetic tape or magnetic disc. A mass storage device has a much larger capacity than main memory. That is, it can store more data or a disc drive.

Output devices receive data from the CPU. The Visual Display Unit (VDU) and printer are common output devices. The VDU is similar to a television screen. The printer produces printed output on paper. Both the VDU and printer present output data for immediate use. Sometimes, the output data is transmitted along a telephone line to another computer. Output data can also be stored for future use on a mass storage device, such as magnetic tape or magnetic disc.

Input devices, output devices and mass storage devices are collectively called Input-Output Devices (I-O Devices), or peripherals.

The second part is software – the programs that control and coordinate the activities of the computer hardware and that direct the processing of data.

For the computer system to operate, computer programs are required. A computer program is a set of instructions for the CPU. These instructions tell the CPU where to find the input data in the system. The CPU is also instructed how to process the data and where to put the results. Programs are not hardware, as they have no electrical or mechanical components. They can be easily changed according to the needs of the user.

Computer software can be divided into two very broad categories - systems software and application software.

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