Classification of Computers – JSS2 Computer Studies Lesson Note (First Term)

Computers are classified by size into four groups: supercomputers, mainframe computers, minicomputers and microcomputers.

Behavioural objectives

By the end of the lesson, students should be able to:

1. list the four classes of computer based on size;
2. describe each class of computer;
3. state where each class of computer is used;
4. name the types of personal computer.

How are computers classified by size?

There are four classes of computer by size: supercomputer, mainframe computer, minicomputer and microcomputer.

1. Supercomputer: the most powerful class.
2. Mainframe computer: large and powerful, but less so than a supercomputer.
3. Minicomputer: smaller than a mainframe.
4. Microcomputer: the smallest and least expensive class, also called the personal computer.

What are supercomputers?

Supercomputers are the most powerful computers, used for problems that need very complex calculations.

• Scientific use: they are widely used in applications such as aerodynamic design simulation and geological data processing.
• Rarity: because of their size and expense, supercomputers are relatively rare.
• Users: universities, government agencies and large businesses.

What are mainframe computers?

Mainframe computers are large computers that are usually slower, less powerful and less expensive than supercomputers.

• Banks and businesses: they use mainframes to update inventory and for similar tasks.
• Many users: they can support hundreds or thousands of users, handling massive amounts of input, output and storage.
• Large organisations: they suit places where many users need access to shared data and programs.
• E-commerce servers: they handle transactions over the Internet.

What is time sharing?

Time sharing is a technique that allows many people at terminals to access the same computer at one time.

• Terminal: a device with a screen and keyboard that connects a user to the main computer.
• Benefit: one large computer serves many users, so each user does not need a separate computer.

What are minicomputers?

Minicomputers are general-purpose computers that are smaller than mainframes and give computing power without the very high cost of larger systems.

• Ease of use: they are generally easier to use than mainframes.
• Terminals: they usually have multiple terminals.
• Servers: they may be used as network servers and Internet servers.

What are microcomputers or personal computers?

A microcomputer, or personal computer, is the smallest and least expensive of all the computers.

• Memory and power: microcomputers have the smallest memory and less power.
• Size: they are physically smaller than the other classes.
• Peripherals: they permit fewer peripherals (devices such as printers) to be attached.
• Name: they are more commonly known as personal computers. The term “PC” is applied to IBM PCs or compatible computers.
• Desktop computers: the most common type of PC.
• Notebook (laptop) computers: used by people who need the power of a desktop system but also want portability.

What are the types of personal computer?

There are four types of personal computer: desktop, laptop, palmtop and PDA.

• Desktop: stays on a desk, with a separate monitor, keyboard and system unit.
• Laptop: a portable computer that folds shut and can be carried about. It is also called a notebook.
• Palmtop: a computer small enough to be held in one hand.
• PDA: a Personal Digital Assistant, a small handheld device for tasks such as keeping a diary and contact list.

How do the four classes of computer compare?

The table below sets the four classes side by side, from the most powerful to the smallest.

Evaluation

1. List the four classes of computer based on size.
2. Which class of computer is the most powerful?
3. What is time sharing?
4. State two uses of mainframe computers.
5. Name the types of personal computer.

Assignment

1. Write two differences between a mainframe computer and a microcomputer.
2. State two uses of minicomputers.