What are Computers

Computers, types, classes

IT, Business Software, Office Automation and Database management Systems Lecture 2, his is very first topic of the computer science and information technology in which we will define computer, stored programs, input/output and many basic level computer concepts. Let’s start with defining with “what is computer”.

What is computer?

“Computer is an electronic digital machine that takes input data and instructions from user, process data according to given instructions, and produce useful information back to user”. This is the simplest way we can define computer.

Key terms to understand


  • Electronic digital means, it works with electronic and digital format of data and instruction.
  • Data means the raw facts about any problem.
  • Entering data and instructions into computer is called inputting and data and instructions both collectively known as “Input”.
  • Performing arithmetic or logical operation on given data as per given instructions is termed as “Processing”.
  • Information is a processed form of data which is produced as “output”.
  • Questions still to be answered
  • Is computer a dumb device?
  • How does a computer perform processing? (Stored Programs)
  • How does a computer understand data and instructions?(binary form)
  • Are there any other forms of computers?(yes)

 Types of computers

There are three types of computers found in literature on the basis computers work and transform data into useful information.

Digital Computers

Such computer that takes input in the form digits with the help of digital signals, can work on programmed input and produce output in the form of digits. Data, instructions and information is manipulated in digits form.  Digital watch, calculator, mobile and personal computers are examples of digital computers.

Analog Computes

The computers which work on continuous and analog type of physical measurements are called analog computers. These computers show output in the form of measurement scale or graph. Analog signals are used to interpret data, instructions and information. ECG machine, Weather forecast Machine etc.

Hybrid Computer

The computers having both type of capabilities of analog and digital computers are called hybrid computers. They can take work on continuous and discrete quantities and can present results in both digits and graphs. Today petrol pumps machines, Glucumeter for sugar level checking and Microwave Oven controllers are best examples of hybrid computers.

Classification of computers

On the basis of power, memory and speed computer can be classified as follows

  • Super computers
  • Mainframe computers
  • Mini Computers
  • Micro Computers

Super Computers

The most powerful and fastest computers of the world are called Supper Computers. Super Computers  titan-3-79578_640are made for highest rate of performance and data processing. They are not general purpose computers that can perform varied type of processing. They perform specialized tasks with some specific for big organizations. The most common example is the NASA which uses super computers for his space projects. Very large in size (room), very expensive and require large Air conditioned environments. Parallel processor are used to design super computers.

See Also: Top ten Supercomputers with HD pictures

Mainframe Computers

Mainframes are not as powerful as supercomputers but these computers are same in design and other features. These computers are relatively less expensive, less powerful and less speedy than supercomputers. These are used in different business firms & government organizations. For Example In Pakistan according to news, NADRA is using Mainframe computers.

Popular Mainframe computers

  • Fujitsu’s ICL VME
  • Hitachi’s Z800

Mini Computers

Mini Computers are also called midrange computers or midrange servers. As the name suggests the mid of Mainframe and the Supercomputer. These computers are designed for a multi users.  hundreds of users can use one mini computer at a time. Individual departments of a oganizations use Mini-computers for specific purposes. For example, a production department can use Mini-computers for monitoring certain production process.

Popular Minicomputers

  • K-202
  • Texas Instrument TI-990
  • SDS-92
  • IBM Midrange computers


A computer made for use of one person at a time is called microcomputer. Desktop computers, laptops, personal digital assistant (PDA), tablets & smartphones are all types of microcomputers. This is the most commonly classification of computers used widely. These computers are the cheapest among all previous categories. Well known manufacturers of Micro-computer are Dell, Apple, Samsung, Sony & Toshiba.

Desktop computers, Gaming consoles, Sound & Navigation system of a car, Netbooks, Notebooks, PDA’s, Tablet PC’s, Smartphones, Calculators are all type of Microcomputers.

History of computer

  • Neiper Bones
  • Pascaline
  • Differene Engine
  • Analytical Engine
  • IBM Moden PC

theiteducation.com References:



Author: Habibullah Qamar

Its me Habib Ullah Qamar working as a Lecturer (Computer Sciences) in Pakistan. I have an MS(M.Phil) degree in computer sciences with specialization in software engineering from Virtual University of Pakistan Lahore. I have an experience of more than 15 years in the filed of Computer Science as a teacher. Blog Writing is my passion. I have many blogs, This one is special made with the aim of providing 100% Free online coaching and training to the students of under-graduate and postgraduate classes. Most of the students enrolled in computer sciences, information technology, software engineering and related disciplines find it difficult to understand core concepts of programming and office automation. They find difficult in understanding and solving their assignments.

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