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What is a Computer?- Classification and anatomy of computer



It is a device used for collecting, storing, correlating, and processing user information at a higher speed and with greater accuracy. A computer typically performs its work by accepting the input from the user, processing the input into some useful information by applying some predefined rules (programs) to it, and eventually producing the output.


Characteristics/Features of a Computer

Computers often come in varied sizes and types. However, they share common characteristics such as cost, performance, speed, reliability, and storage capacity.

Cost: The computers can be distinguished or classified based upon their associated cost and size.


Speed: All the computers have their own individual processing speed. This speed depends upon the type of computer being used. For example, the mainframe computers have a speed of 18000 MIPS (Million of Instruction Per Second).

Performance: The performance of the computer includes its processing speed, accuracy, and reliability. The performance parameters vary depending on the type of computer being used. A typical PC offers less performance compared to a supercomputer which in turn offers significantly more performance than a mainframe system.


Reliability: Reliability is one of the significant characteristics of a computer system. The performance of the system depends to a great extent on the reliability of the system in producing the results. A computer system of the present generation is much reliable in terms of storage and processing. The results obtained by using a computer are much accurate and faster than the results obtained manually.

Storage Capacity: The present typical computer offers a maximum storage capacity of 500 GB which means that multimillion files including documents, music, animation clips, movies, etc., can be stored at a single location thereby eliminating an overhead involved in maintaining thousands of paper files.


Classification of Computers Based on Size 

A computer is a fast electronic device, which takes the input in the form of instructions, process it and finally produces the output. A computer can be classified into various types depending on various parameters like speed, capacity, data transfer rate, process etc. Based on the parameter size, a computer is classified into following four types, 

  • Super computers  
  • Mainframe computers  
  • Micro computers  
  • Mini computers. 
Types of computer (based on size)
Types of computer (based on size)

1.Super Computers 

Super computers are those computers which are designed with high speed processing capabilities and huge storage capacities. They are the first largest general purpose computers that are capable of performing several billions of calculations per second. The processing speed of these computers is very fast as they comprises of multiple CPU’s that operates concurrently. These computers generally occupy large rooms and are operated by many professional engineers. 

Super computers are mainly used in 


(a) Weather forecasting 

(b)Nuclear energy research 


(c)Designing of machines, weapons, supersonic aircraft etc. 

Examples: Some examples of super computers are CRAY, PARAM and PACE. 


2. Mainframe Computers 

Mainframe computers are second largest, ultra high performance computers. These computers are designed to compromise with large scale needs of business organization. These systems are capable of storing and processing huge amount of data. A mainframe computer consists of following components. 

(a) High speed computer processor 


(b) Peripheral devices to support massive volume of data processing 

(c) High performance online transaction processing systems. 


(d) Extensive data storage and retrieval system equipments. 

Mainframes computers are used in large business organizations as well as in scientific areas. 


Examples: Some examples of mainframe computers include IBMs, ES000, VAX 8000 and CDC 6600. 

3. Micro Computers 

Micro computers are smaller in size inexpensive general purpose digital computers. These computers consist of components like microprocessors, storage unit, input channel, output channel mounted on a single chip. These computers can be used by individual users in homes, educational institutions, small business organizations etc. 


Examples: Some example of micro computers include IBMPC pentium 100, IBM-PC, Apple Macintosh, desktop, Laptops hand-held computers etc. 

(A)Desktop Computers/Personal Computers 

Desktop computers are used by individual users from a single location. These types of computers are affordable. These computers are used in small business organizations, educational institutions, homes, railway department hospitals etc. Personal computers consist of following components. 

  • Monitors 
  • Keyboard 
  • Mouse 
  • Internal hard disk 
  • Other peripheral devices. 


Laptops are smaller in size and portable computers. These computers are basically preferred while travelling. These computers consists of rechargeable battery and doesn’t require any external power supply. 

(C)Hand-held Computers or PDA 

Hand-held computers are very small in size and can be stored in a pocket. These computers uses pen or electronic system as an input device rather than keyboard. Handheld computers uses small cards for storing data as well as program files. They are bigger in size than a conventional calculator. 4. Mini Computers 

4.Mini Computers 

Mini computers are types of digital computers that are capable of storing data more than micro computers. These computers are mainly designed with dual processor. The main purpose of these computers is to carry out auxiliary operations by connecting to mainframes with speed and efficiency. They are considered as centralized store house or network server. Mini computers are used in, 


(i) Industries  

(ii) Educational institutions  


(iii) Research organizations 

(iv) Small or medium business organization. Example 


Examples: Some examples of mini computers are PDPII, IBM (8000 services) and VAX 7500. 

What is a Computer

A computer system comprises of the following essential components


The devices that are used to insert the data into the computer are called the input devices. Various devices are available for inputting the data on graphics workstations. Keyboard is known as most commonly used Input Device among all input devices. Other special input devices includes mouse, trackball, spaceball, joystick, dials, digitzers, data globes, button boxes, image-scanners, voice systems and touch panels.

(a) Keyboard

Keyboard is used to enter data and commands which is in data and alphabet form. It is also used to enter the screen coordinates, to select the menu-options or graphic functions etc. A regular Keyboard consists of 101 keys.



Mouse is a small hand-held device that is used to position the screen cursor. It has two rollers (wheels) at the bottom which are perpendicular to each other and are used to determine the amount and direction of the mouse movement. The two wheels are connected to a shaft encoder which generates an electrical signal on each rotation of the wheel. The mouse movement is encoded in x and y directions, when it is moved on a flat surface and stored in a separate registers.

(c) Trackball

Trackball is a 2D positioning device that is fixed in its base and can be rotated with fingers to generate screen-cursor movement.


(d) Joystick

Joystick is similar to a trackball, but has limited movement. It consists of a stick (i.e., a small and vertical lever) that is attached to the base and is used to direct the cursor.

(e) Data Glove

Data glove is an input device that is used to hold the virtual object and also determines the motion of the fingers and the hand by using a set of sensors.


(f) Touch Panels

Touch panels are the input devices involve the selection of an object or screen positions with a finger touch.

Example: Option selection using a graphical icon.


(g) Light Pens

Light pens are the input devices that are used to select the screen position by detecting the light incident on the screen when placed perpendicularly to the screen. Output


Output devices are those devices, using which a computer can communicate with the users. These devices takes the result which is in machine-language from the processor and translate these results in the form easily understood by the users.


Types of Output Devices

  • Display screens
  • Printers
  • Plotters.

(a) Display Screens

Display screens or monitors are output devices that not only display the programming instructions but also display the data supplied as input. Printers

(b) Printers

Printers are hard copy output devices that print both information and data consisting of characters, symbols, graphics on paper or on some other durables surface like microfilm. Some printers are text-specific while others can print graphics also. ) Plotters


(c) Plotters

Plotters are used for creating vector images by using a pen which is attached to a computer. Because of this, plotters are referred to as penbased output device.

3.Central Processing Unit (CPU)

CPU(Central Processing Unit) is the brain of computer system. It performs the following,

  1. Interprets the operations
  2. Coordinates the operations
  3. Supervises the instructions
  4. All the internal and external peripherals are controlled by this unit
  5. Controls the computer’s functions
  6. Performs all calculations (Arithmetic and Logic)
  7. Processes all user-entered data.

Components of CPU

(a) Arithmetic Logic Unit

(b) Control Unit


(c) Memory Unit

(d) Registers.


(a) Arithmetic Logic Unit

Arithmetic and logical operations are performed in this unit.

(b) Control Unit

This unit is responsible for controlling the operations sequence.


(c) Memory Unit

This unit stores the intermediate result obtained during the calculations and provides the data to the user depending on their requirements.

(d) Registers

Registers are considered as special purpose, highspeed temporary memory components that are capable of storing different types of information like data, instruction, addresses etc. It generally store that information which is currently being used by CPU.


Types of Registers

The following are different types of registers,


(i) Program Counter (PC) Register

(ii) Instruction Register (IR)


(iii) Memory Address Register (MAR)

(iv) Memory Buffers Register (MBR)


(v) Accumulator (ACC)

(vi) Data Register (DR).



Memory is a storage area in a computer used for storing data or programs on temporary or permanent basis. Memory is categorized as two types which are listed below.

(a) Primary memory


(b) Secondary memory.


By this article one can understand the complete information on computer right from the classification to anatomy. Hope you like this article and can continue reading more articles on tech such as How “Tesla cars” are being at the top in the race of electric vehicles.?



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