Classification of Computers by Size

Supercomputers
Mainframe computers
Minicomputers
Personal computers (PCs) or microcomputers
Supercomputers

A supercomputer.
Supercomputer – a powerful computer that can process large amounts of data and do a great amount of computation very quickly.
Supercomputers are used for areas related to:
Science
Engineering
Education
Defence
Aerospace
Supercomputers are useful for applications involving very large databases or that require a great amount of computation.
Supercomputers are used for complex tasks, such as:
Weather forecasting
Climate research
Scientific simulation
Oil and gas exploration
Quantum mechanics
Cryptanalysis
Mainframe computers

A mainframe computer.
Mainframe computer – a high-performance computer used for large information processing jobs.
Mainframe computers are primarily used in :
Institutions
Research
Academics
Health care
Libraries
Large businesses
Financial institutions
Stock brokerage firms
Insurance agencies
Mainframe computers are useful for tasks related to:
Census taking
Industry and consumer statistics
Enterprise resource planning
Transaction processing
e-business and e-commerce
Minicomputers

A minicomputer.
Minicomputer – a mid-range computer that is intermediate in size, power, speed, storage capacity, etc., between a mainframe and a microcomputer.
Minicomputers are used by small organizations.
“Minicomputer” is a term that is no longer used much. In recent years, minicomputers are often referred to as small or midsize servers (a server is a central computer that provides information to other computers).
Personal computers

A personal computer.
Personal computer (PC) – a small computer designed for use by a single user at a time.
A PC or microcomputer uses a single chip (microprocessor) for its central processing unit (CPU).
“Microcomputer” is now primarily used to mean a PC, but it can refer to any kind of small computer, such as a desktop computer, laptop computer, tablet, smartphone, or wearable.
Types of personal computers

Desktop computer – a personal computer that is designed to stay at one location and fits on or under a desk. It typically has a monitor, keyboard, mouse, and a tower (system unit).
A desktop computer.

Laptop computer (or notebook) – A portable personal computer that is small enough to rest on the user’s lap and can be powered by a battery. It includes a flip down screen and a keyboard with a touchpad.
A laptop computer.

Tablet – A wireless touchscreen PC that is slightly smaller and weighs less than the average laptop.
A tablet computer.

Smartphone – A mobile phone that performs many of the functions of a personal computer.