Categories of Computer

Normally, computers are categorized on the basis of size, speed, processing power and price. However, categorizing computers is not very straight-forward. The distinction between these categories is sometimes not very clear. Sone characteristics overlap different categories. Computers can be divided into the following categories:

Personal Computers / Micro Computers

Personal computer is a type of computer that performs input, output, processing and storage activities by itself. It consists of input device, output device, storage device, memory and processor. It generally consists of single processor. However, some personal computers may have multiple processors. Most commonly used personal computers are PC and Apple Macintosh. The price of personal computer is from $500 to $5000.

Personal computers have different processors and operating systems. PC and its compatible computers use Windows operating systems. Apple Macintosh and its compatible computers use Macintosh operating system also called Mac OS.

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PC and its compatible computers follow the specifications of the original IBM personal computer. Some PC compatible computers include Compaq, Dell and Toshiba. Following are different types of personal computers.

Desktop Computers

Desktop computers are the most common type of personal computer. It is designed in a way that all its components fit on a desk or table. In one model, the system unit is placed horizontally on the desktop or table and monitor is placed on the system unit. In another model, called tower model, both monitor and system unit are placed on the table. The system unit in the tower model is placed vertically.

Different desktop computers are as follows:

All-in-One Computer: It is a less expensive computer. In this computer, monitor and system unit are combined into single device.

Workstation Computer: It is more expensive and powerful computer. It is used for calculations and graphics work. It is mostly used by engineers, graphics artists and architects.

Stand-alone Computer: It is a computer that performs input, output, storage and processing activities by itself without being connected to other computers. However, many stand-alone computers also have networking capabilities.

Server Computer: It is a computer that manages the resources of a network. It controls access to the software, hardware of the network. It also provides a centralized area to store data, information and software.

Notebook Computers

A notebook computer is also called a laptop computer. A laptop computer is very small in size and can be placed easily on a lap. Only one user can use them at a time. It uses less power. It can be used using batteries.

Notebook computers can be brought anywhere easily because of lightweight. Its weight is generally around 2KG. These computers are frequently used in business. Laptop computers are more expensive than desktop computers. In notebook computer, the keyboard is placed on the top of the system unit. The cost of these computers is from $1000 to $2500.

Tablet PC

Tablet PC is a special type of notebook that works with a digital pen. The user gives instructions with digital pen. It can also use keyboard for input. It also supports voice input.

Tablet PC is used to take notes in lectures, meetings, conferences etc. Another type of Tablet PC is called a modular computer. It is small enough to fit in the hand.

Handheld Computers

Handheld computer is also known as a palmtop computer. It easily fits in the hand of the user. It contains small screen and small keyboard. Some handheld computer have no keyboard at all. Handheld computers usually have no disk drive. The programs and data are stored on chips in the system unit.

Handheld computer can be connected to a large network to exchange data. Some use the stylus as input device to enter text and draw lines etc. Some handheld computers also recognize voice input. The user can enter text and instruction by speaking. Some examples of handheld computers are as follows:

Personal Digital Assistant (PDA) – PDA is used to organize personal information. It provides the facilities of calendar, appointment book, address book, calculator and notepad. Some PDAs provide word processing and spreadsheet functions.

Web-Enabled Cellular Telephone – It is also called smart phone. It is used to send and receive messages on the Internet. It can also browse websites that are specially designed to be used on the cellular phones.

Web-Enabled Pager – It is also known as smart pager. It is a two-way radio. It is used to send and receive messages on the Internet.

Difference between Desktop and Portable Computer

The difference between desktop and portable computer are as follows:

Desktop ComputersPortable Computers
It cannot be used in mobile computing.It is designed for mobile computing.
Its cost is lower.Its cost is higher.
It can be expanded easily.It cannot be expanded easily.
Its repair services are easily available.Its repair services are not easily available.
The use of mouse and pointing devices use of mouse and pointing devices is easyThe use of mouse and pointing devices is difficult.
It can use all current PC chips.Some models cannot use all PC chips due to cooling problems.
It has the capability of high RAM and hard drive.It has the capability of comparatively less RAM and hard drive.

Internet Appliances

Internet appliance is also known as an information appliance. It is a computer that is used to connect to the Internet from home. It contains all software applications required to connect to the Internet and browse.

The set-top box is one of the most popular Internet appliances. It is used to access the Internet and browse websites using a device similar to remote control. It is connected to the television set to view web pages.

Mini Computers

Minicomputer is larger and more powerful computer than personal computer. It can execute five million instructions per second. It generally consists of two or more processors. It is more reliable than desktop computer but not as solid as mainframe. Mini computers were introduced in 1960s. Minicomputers are also called mid-range servers.

Mini computer can serve up to 4000 connected users simultaneously. It is normally accessed by users via personal computer or terminal. A device with a monitor and keyboard is called terminal. It is also known as a dumb terminal. It has no processing power and cannot work as a stand-alone computer. It has to be connected to a server.


Examples of midrange servers are:

  • Prime 9755 VAX 8650
  • IBM System 360
  • AS 400

Uses of Mini Computers

Mini computers are often used by small and medium-sized companies or departments to provide a centralized store of information and computer programs.

Mainframe Computers

A mainframe computer is a large computer in terms of price, power, and speed. It is more powerful than a mini computer. It consists of multiple processors. It is specially designed to perform multiple intensive tasks for multiple users simultaneously. It is designed for high reliability. It can be serviced and upgraded while it is running. It is also known as enterprise server.

Mainframe computers can serve up to 50,000 users simultaneously. These computers wn store large amounts of data, information and instructions. The users access a mainframe computer through terminal or personal computer.

A typical maintrame computer (an execute 16 million instructions per second. Qualified operators and programmers are required to use these computers. Mainframe computers can accepl all types of high-level languages. Different types of peripheral devices can be attached with mainframe computer.


Examples of mainframe computers are

  • IBM4381
  • NEC 610
  • DEC 10

Uses of Mainframe Computers

Mainframe computers are used in large organizations such as banks, educational institutions, financial institution, and atomic research centers. For example, airlines use these computers to maintain flight schedules, ticket reservation system, etc. Govt. agencies such as NADRA use mainframe computers to maintain the information of the population. Many shopping chains interconnect their stores with mainframe computer to track transactions immediately and maintain stock.

Super Computers

Super computer is a state-of-the-art machine. It is the biggest in size and the most expensive in price than any other computers. It is the most sophisticated, complex and advanced computer. It has a very large storage capacity. It can process trillions of instructions in one second. The modern super computer consists of thousands of microprocessors. Supercomputer uses high-speed facilities like a satellite for online processing.


Examples of supercomputers are as follows:

  • ETA-10
  • Deep Blue
  • Asci White

Uses of Super Computers

Super computer is mostly used for weather predictions, weapon design, preparing models of a chemical and biological system, mapping the surface of planets and studying the neural network of the brain.

Super computer is also used in business and industry field. For example, aircraft manufacturers use it to simulate aircraft and check it performance.

Governments use super computer for different calculations and heavy jobs. Many Hollywood movies use it for animation purposes.

Difference among Micro, Mini & Mainframe Computers

The difference between desktop and portable computer are as follows:

Micro ComputerMini ComputerMainframe Computer
It was introduced in 1970It was introduced in 1960It was introduced in 1975.
Its generally consists of one processor.It generally consists of two or more processors.It generally consists of multiple processors.
Its storage capacity is in GB.Its storage capacity is in TB.Its capacity is in TB.
Its memory is in MB.Its memory is in GB.Its memory is in GB.
It can normally be used by 1 user at a time.It can serve two to thousands of connected users at a time.It can serve hundreds to thousands of connected users at a time.
Its size is very small.Its size is bigger than the microcomputer.Its size is bigger than micro and minicomputers.
Its price is $500 to $5000.Its price is $18000 to $500000.Its price is $500000 to $5 million.
It is used at home, offices and educational institutes.It is used by business institutes and departments.It is used by large organizations like banks.
Examples are IBM-PCs and Apple MacintoshExamples are VAX-8800.Examples are IBM-370 and MV-1500 NEC

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