Computer Science

Classification of Computer

Computers are classified on the basis of size, speed, processing power, and price. However; the classification of computers is not very straightforward. The distinction between these categories is sometimes not very clear. Some characteristics overlap different categories. Computers can be classified into the following categories:

  1. Personal Computer
  2. Mobile Devices
  3. Minicomputer
  4. Mainframe Computer
  5. Supercomputer
  6. Embedded Computer

Personal Computers / Microcomputers

A personal computer is designed to be used by one person at a time. It consists of a processor, memory, and one or more input, output, and storage devices. It also often contains a communication device. Personal computers are available in different sizes and shapes.
The personal computer IS commonly used in business, at home, and other fields of life. The price of a personal computer is from several hundred to several thousand dollars.

The most commonly used personal computers are PC and Apple PC and their compatible computers use Windows operating systems. Apple computers use Mac OS operating system. PC and its compatible computers follow the specifications of the original IBM personal computer. Different companies such as Dell, Acer, HP, and Asus sell PC and compatible computers.. Significant types of personal computers are desktop and portable 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 the monitor is placed on the system unit. In another model, called the tower model, both the monitor and system unit is placed on the table. The system unit in the tower model is placed vertically. Some desktop computers also have touch screens.

Different desktop computers are as follows:

1. All-in-One Computer

An All-in-one computer combines a monitor and system unit into a single crevice. It does not have a separate tower. Many all-in-one models, also have touchscreen technology. These computers save desktop space. HP TouchSmart and Apple iMac are examples of all-in-one-computer.

2. Workstation Computer

A workstation is a more powerful and expensive desktop computer. It is used for calculations and graphics work. A workstation can perform tasks that require a lot of processing speed. It is mostly used by engineers, graphics artists, and architects. For example, architects use workstations to design buildings and homes. Graphic artists use workstations to create animations and special effects for movies and video games.

3. Server Computer

A desktop computer can be used as server. A server computer provides services and controls access to
the hardware, programs, and data in the network. It also provides a centralized storage area for programs, data, and information.

Portable Computer

A portable computer is a mobile personal computer that can be carried from one place to other easily. It has input, output, storage, and processing components integrated into a single unit. It can receive power from an electrical outlet or a battery.

Portable computers are affecting our daily routine in this modern era both positively and negatively. People
can use a mobile computer anywhere at home, in the office or classroom, and during travel, etc. Businessmen can use it during travel to manage and monitor business activities. The students can use it in class to perform different
educational activities. A salesperson can use it to give presentations to clients and store information about them anywhere. However, portable computers are creating some negative effects as well. People use them frequently to stay online, play games and chat, etc. It affects social interaction among people.

Different types of portable computers include laptops and tablets.

1. Laptop

A laptop is a mobile computer that has a keyboard, screen, and other devices integrated into a single compact case. It is designed to fit in the lap. It uses less power than desktop computers and can be used outdoors without the need for an electrical outlet. It has batteries and can be used for many hours without a continuous power supply. It typically has a built-in wireless communication facility. Some laptops come with touch screens. The laptop is also known as a notebook computer.


It is a thin, lightweight, and full-featured laptop with high-end processing and video capabilities. It typically uses a solid-state drive (SSD) so it boots up very fast. It uses very less power and provides longer battery life than a traditional laptop. It does not have an optical drive. Some examples of ultrabooks are Apple MacBook Air and Asus ZenBook.


It is a small, lightweight and inexpensive laptop computer. It has longer battery life than a laptop. It has built-in wireless capabilities. It is suitable for general computing and web-based applications. It has limited memory and storage. It provides reduced computing power as compared to a full-size laptop computer. It has no optical drives.

2. Tablet

Tablet is a thin and lightweight mobile computer with a touch screen, It is usually smaller than a laptop. Some tablets include a stylus that looks like a small pen. It can be used to enter data and select different objects on the screen. A physical keyboard can also be attached to a tablet. It provides longer battery life than a laptop. The Apple iPad is an example of a tablet computer.

Tablet comes with a variety of pre-installed programs called mobile applications or mobile apps. It can be used to browse the web, send and receive emails and watch videos, etc. There are extensive collections of applications for tablets that can be downloaded on tablets for free or for a small price.

Two basic designs of tablets are Slate and Convertible.

1. Slate

This type of tablet does not contain a physical keyboard. It uses an on-screen virtual keyboard for input. The user can also attach a physical keyboard with Bluetooth or wireless.

2. Convertible

This type of tablet has a display screen attached to a keyboard. It can be rotated 180 degrees and folded down over the keyboard. It can be repositioned to look like a notebook computer.

Mobile Devices

A mobile device is a computing device designed to hold in the hand. Mobile devices typically have small screens and some of them have keyboards. Mobile devices usually have no disk drives. The programs and data are permanently stored on special memory or on a small storage media such as a smart card. Mobile devices can be connected to large networks to exchange data. Mobile devices are almost always powered by a rechargeable battery system. It has built-in wireless connectivity for Internet access. Popular types of mobile devices are smartphones, handheld computers, portable media players, and e-books.

1. Smartphone

A smartphone is a cell phone that includes many features of a computer and can run general-purpose computing applications. Many smartphones have touch screens to input data using a fingertip or a stylus. Some have a built-in mini keyboard. iPhone is an example of a smartphone.

Some features of smartphones are as follows:

  • Internet access
  • Make and answer phone calls
  • Send text messages, picture messages, and video messages
  • Personal information management such as calendar, address book, and calculator, etc.
  • Send and receive email messages
  • Communicate wirelessly with other devices or computers
  • Built-in camera to share images
  • Conduct live video calls or videos with others
  • Play and organize music
  • Voice recording
  • GPS services
  • Computing power to run programs like word processors etc.

2. Handheld Computers

A handheld computer is a small, lightweight computer that easily fits in the hand. Many handheld computers communicate wirelessly with other devices or computers. Some have small keyboards and others have a touch screen and also include a stylus for input. Many handheld computers are used by mobile employees such as parcel delivery people or warehouse employees to take inventory and check supplies etc.

A handheld computer is not very powerful and cannot perform many tasks that can be performed by desktop and
notebook computer.

3. Portable Media Player

A portable media player is a mobile device designed to store, media. Digital media includes music, photos, and videos. These devices offer cameras, access to the Internet, and a variety of applications.

Some portable media player models have a touch screen or touch-sensitive pad. A touch-sensitive pad contains buttons and wheels to be used with a thumb or finger. It can be used to scroll, play music, view photos, watch videos adjust volume, etc. Portable media players usually include a set of earbuds that adjust volume etc. Portable media are small speakers that rest inside a car canal. iPod Touch is an example of a portable media player.

4. E-Book Reader

An E-book reader is designed for reading books, magazines, and other digital publications. It is also called an e-reader. An e-book is an electronic version of a printed book readable on computers and other mobile devices. E-reader devices can hold thousands of e-books.

Most e-readers have a touch screen and built-in wireless technology to connect to the Internet. An on-screen keyboard can be used to navigate, search, and highlight the contents. The user can browse an electronic bookstore and download new ebooks quickly via
a wireless connection.

Some e-readers use e-ink technology. It makes screens easy to read and extends battery life for up to two months. The reader can feel the experience of reading a printed book. The screen can easily be read even in bright sunlight. Some e-readers have LCD screens similar to laptops and tablets. LCD screens can display colors and books with colorful photos. However, it is used to view magazines, and is more difficult to read content in bright sunlight.


A minicomputer is typically larger, more powerful, and more expensive than a personal computer. Minicomputers can serve up to several hundred connected users at the same time. It can be used in a networked environment as a server computer. It is also called a mid-range server. It is normally accessed by users through a personal computer, a thin client, or a dumb terminal. A device with a monitor and keyboard is called a dumb terminal.

Minicomputers are used by small and medium-sized organizations. They provide a centralized store of information and computer programs.


Some examples of minicomputers are as follows:

  • Prime 9955
  • HP 3000
  • AS 400
  • VAX 8600

Mainframe Computers

A mainframe computer is a large computer designed to serve several thousand connected users at the same time. It is more powerful and expensive than a minicomputer. These computers can store large amounts of data, information, and
programs. The users access a mainframe computer through a personal computer, thin client, or dumb terminal. A mainframe computer is also known as an enterprise server or high-ended server.

The price of a mainframe computer can be several thousand dollars to several million dollars. IBM, Sun and Unisys are leading manufacturers of mainframe computers.

Mainframe computers are used in large organizations to manage large amounts of centralized data such as banks, universities, and insurance departments. For example, airlines use them to companies and governments maintain flight schedules, ticket reservation systems, etc. Govt. departments such as NADRA use mainframe computers to maintain the information of the population. Many shopping chains interconnect their stores with mainframe computers to track transactions immediately and maintain stock.


Some examples of mainframe computers are as follows:

  • IBM S-390
  • NEC 610
  • DEC 10
  • IBM System Z10
  • Station Z l0


A supercomputer IS the fastest and the most powerful computer. It is the biggest in size and more expensive than any other computer. It is used to perform complex tasks. It has a very large storage capacity and can store several thousand times more data than an average desktop computer, It also consumes so much energy. The modern supercomputer consists of thousands of microprocessors. It can process trillions of instructions in one second. The cost of one supercomputer can be up to several billion dollars.

The supercomputer is mostly used for weather forecasting, weapon design, and atomic research, etc. The supercomputer is also used in business and industry fields. Aircraft manufacturers use it to simulate aircraft and check their performance. Governments use supercomputers for different calculations and heavy jobs. Many Hollywood movies use it for animation purposes.


Examples of supercomputers are as follows:

  • Roadrunner
  • Blue Gene
  • Deep Blue
  • ASCI White

Embedded Computers

An embedded computer is designed for special purposes. It works as a component in a larger product. These computers are very small and have limited hardware. They perform various functions according to the requirements of the product in which they are embedded.

Embedded computers are used in commonly used products such as:

  • Electronics: PDAs, mobile, video recorders and DVD players, etc.
  • Home Devices: Security monitoring systems & programmable microwave ovens etc.
  • Automobiles: Car engine controller, airbag controller, etc.
  • Process Controllers and Robotics: Machine controllers, blood pressure monitors, etc.

Difference between Desktop & Laptop Computer

The difference between desktop and laptop computers is as follows:

Desktop ComputerLaptop Computer
1. Desktop computer is not portable.1. Laptop computer is portable.
2. It can be upgraded and repaired relatively easily.2. It is relatively difficult to upgrade and repair it.
3. It uses more power than a laptop.3. It uses less power than a desktop.
4. It has no batteries and cannot be used without a continuous power supply.4. It has batteries and can be used without a continuous power supply.
5. It is generally less expensive than a laptop computer.5. It is generally more expensive than a laptop computer.
6. It is typically used in offices as well as at home for personnel use.6. It is typically used at home for personnel use.
7. It normally requires external devices like a keyboard and mouse etc.7. It all normally requires external devices like a keyboard and mouse in a single unit.
8. It is heavier than a desktop computer.8. It is light-weighted than a desktop computer.
9. It typically does not have a built-in wireless communication facility.9. It typically has a built-in wireless communication facility.

Difference between Laptop & Tablet

The difference between a laptop and a tablet is as follows:

1. Laptop is more powerful than a tablet.1. Tablet is less powerful than a laptop.
2. Its hardware can be upgraded.2. Its hardware cannot be upgraded.
3. It has more storage capacity.3. It has limited storage capacity.
4. Its size is bigger than a tablet.4. Its size is smaller than a laptop.
5. It is thicker and heavier than tablets.5. It is thinner and lightweight than a laptop.
6. The user can connect more external devices with a laptop.6. The user can not connect more few devices with a tablet.
7. It does not support applications specifically designed for tablets.7. It does not support applications specifically designed for laptops.
8. It has less battery life than a tablet.8. It has longer battery life than a laptop.
9. It uses a traditional operating system such as Windows and Mac OS etc.9. It uses mobile operating systems such as Android and iOS etc.
10. It normally accepts input using a physical keyboard.10. It normally accepts input using a virtual keyboard with a touch screen.

Difference among Micro, Mini & Mainframe Computers

The difference between Micro, Mini & Mainframe Computers is as follows:

MicrocomputerMinicomputerMainframe Computer
Its speed is less than mini and mainframe computers.Its speed is more than a microcomputer and less than a mainframe computer.Its speed is more than micro and minicomputer.
It can normally be used by 1 user at a time.It can serve several hundred users at a time.It can serve several thousand users at a time.
Its size is small.Its size is bigger than microcomputers.Its size is bigger than micro and minicomputers.
Its price is several hundred to several thousand dollars.Its price is several thousand to million dollars.Its price is several thousand to several million dollars.
It is used at home, offices, and educational insulates.It is used by small and medium organizations.It is used by large organizations like banks.

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