A computer system is a programmable machine designed to store and retrieve information and perform arithmetic and logical operations to produce meaningful results in desired format. It consists of three main units:
Central Processing Unit (CPU) and
Different computers have different ways in which the input, processing and output units are connected. In desktop computers, all three units are separate devices, as shown in figure below. It has:
- A keyboard, which is the input unit
- A box with the Central Processing Unit, which is the processing unit and
- A monitor, which is the output unit.
Input unit helps the user to enter raw data and instructions into the computer system, central processing unit performs the required operations as per given instructions and the output unit produces meaningful results in the desired format for the user.
Central processing Unit (CPU)
The CPU is further divided into three parts:
(i) control unit (CU),
(ii) arithmetic and logic unit (ALU), and
(iii) memory unit (MU).
Control unit acts as a receptionist and a manager of a company. It receives each and every instruction from the user and coordinates between different parts to perform various operations. Arithmetic and logic unit acts as an accountant of a company, which performs all the mathematical and logical calculations and the memory unit acts as a temporary store of a company, where a small amount of data is stored while other operations are being performed.
In a laptop, all three units, input, processing and output are combined into one device. Input and output devices are also called ‘peripherals’. These are plugged into the computer using connection ports.
An input device is used to enter information into the computer. A keyboard is an input device used to enter letters, numbers and control functions. Microphone is an input device that is connected to the computer to record sound. A web camera is a device used to record videos. Many computers come with built-in microphones and webcams. Another input device is a scanner that copies physical documents and stores them in a computer in digital (computer-readable) format. For example, if you fill an admission form for a college, you can scan it and then e-mail it to the college instead of sending the actual form by post.
Output devices bring information from the computer to the user. If you want to calculate the percentage marks, you input all your marks using a keyboard, the computer calculates using the formula and you see the results on a monitor screen. This monitor is the output device on which the computer displays the output information. In the same way, a printer is an output device which gives us the hard copy of the information processed by the computer. If you want to hear the song you have recorded, you can use speakers to play them. Just like input devices, output devices can also be either separate or built-in to the computer. The commonly used peripheral devices are given in table below:
|Keyboard: It is used to provide input to the computer on what to do, which could be in the form of typed letters, numbers, and symbols.||Mouse: We use it to go to different parts of the screen on the monitor.||Microphone: It is used to record voice on the computer, and communicate.||Projector: It is used to project images or video from a computer on a screen.|
|Monitor: It displays all the visual output that the CPU produces after processing the input.||Speakers: It plays back all the soundbased output.||Scanner: It is a device that scans/ captures a paper image, document and converts it to a digital file on the computer.||Printer: It helps to print out the visual output on the paper, as displayed on the monitor.|