According to Unitechstar, Computers differ based on their data processing abilities. They are classified according to purpose, data handling and functionality. According to purpose, computers are either general purpose or specific purpose. General purpose computers are designed to perform a range of tasks.
According to Unitechstar,Today computers come in a wide variety of sizes, capabilities, designs and what have you, that it makes it difficult for one to easily classify them.
We have types of computers today ranging from :Tiny computers embedded in consumer devices and appliances,Pocket-sized computers and mobile phones that perform limited computing functionalities,The powerful and versatile desktop and portable computers used in homes and businesses,To the super powerful computers used for high demanding computing capabilities like controlling a country’s defense systems.Generally, computers are classified into many categories based on their size, capacity, purpose and type. In this post we talk about classification of computers based on the size and capacity.
Classification Of Computers By Size And Capacity
When classified according to size and capacity, the following types of computers can be identified: supercomputers, mainframe computers, minicomputers, microcomputersand embedded computers.
Supercomputers
Supercomputers are the most powerful and physically the largest by size. These are systems designed to process huge amounts of data and the fastest supercomputers can perform over one trillion calculations in a second. 
Supercomputers like the Cray T90 system has thousands of processors. Supercomputers cost very high and are therefore only used by large corporations, government agencies and universities that can afford them. Because of their extraordinary speed, accuracy and processing power, supercomputers are well suited for solving highly complex problems and performing tasks that demand huge amounts of calculations. The following functions are some of those performed by supercomputers: space exploration and sending of astronauts into space; controlling missile guidance systems and satellites for national defense; oil exploration; hosting extremely complex web sites and decision support systems for organizations; etc.
Mainframe Computers
Mainframe computers are very large often filling an entire room and can process thousands of millions of instructions per second. They are used in larg
e private and government organizations like insurance companies and banks where many people need frequent access to information. In a mainframe environment, users connect to the mainframe through the many terminals wired to the mainframe. Mainframes are capable of supporting hundreds to thousands of users simultaneously. Some of the functions performed by a mainframe include: flight scheduling, reservations and ticketing for an airline; government agencies such as the Internal Revenue Service, Electoral Commission and the Census Bureau use mainframes to track information about large populations, vote computations, individual tax records, payroll, etc.; many large grocery and retail companies use mainframes to register sales, update stock and manage inventory levels.
e private and government organizations like insurance companies and banks where many people need frequent access to information. In a mainframe environment, users connect to the mainframe through the many terminals wired to the mainframe. Mainframes are capable of supporting hundreds to thousands of users simultaneously. Some of the functions performed by a mainframe include: flight scheduling, reservations and ticketing for an airline; government agencies such as the Internal Revenue Service, Electoral Commission and the Census Bureau use mainframes to track information about large populations, vote computations, individual tax records, payroll, etc.; many large grocery and retail companies use mainframes to register sales, update stock and manage inventory levels.Minicomputers
Minicomputers are m
uch smaller than mainframes and are also less expensive. Sometimes referred to as Midrange Server or Midrange Computer, they are typically larger, more powerful and more expensive than desktop computers. Midrange computers are usually used by small and medium-sized businesses as their servers. Users connect to the server through a network by using desktop computers, notebooks, thin clients or dumb terminals. They are also used by hospitals as well as in school computer laboratories.
uch smaller than mainframes and are also less expensive. Sometimes referred to as Midrange Server or Midrange Computer, they are typically larger, more powerful and more expensive than desktop computers. Midrange computers are usually used by small and medium-sized businesses as their servers. Users connect to the server through a network by using desktop computers, notebooks, thin clients or dumb terminals. They are also used by hospitals as well as in school computer laboratories.Microcomputers
Microcomputers are the most frequently used type of computer. Also, known as Personal Computer (PC), a microcomputer is a small computer system designed to be used by one person at a time. The size of microcomputers range from those that can fit on a desktop, inside a briefcase, or even into a shirt pocket. The various sizes of microcomputers can be grouped into desktop computers and portable computers.
- Desktop computers are the conventional ones which fit on a desk
and usually consists of a system unit, monitor, keyboard, and a mouse. These computers have desktop cases designed to be placed horizontally on a desk’s surface, usually with the monitor sitting on top of the system unit. Today the most common type of desktop computer uses a system unit called the Tower which is designed to sit vertically on the floor or the table.
Portable computers are microcomputers designed to be carried easily around in the hand, bag, 
briefcase or pocket depending on their sizes. They run on rechargeable batteries and also use an adapter which allows them to be plugged into a power outlet to be recharged. Portable computers are essential for many workers like salespeople, agents and managers who may be off-sites and in remote locations but need computing and communications resources as they travel. Many students are also increasingly purchasing portable computers as their primary home computers. The types of portable computers that are about the size of a standard paper notebook are called Laptop or Notebook c
omputers. They are fully functioning computers that open to reveal a screen and a keyboard. Another type of portable computer is the Tablet PC or simply Tablet which is contained in a touchscreen panel. Most Tablets are a little smaller and weigh less than the average laptop. Earlier Tablets required stylus but modern ones are operated by fingers and a stylus is an option. Handheld computers are also portable. They are about the size of a pocket calculator and have built-in keyboard or thumb pad. Some also accept input through digital pen or touch. Examples are the Personal Digital Assistant (PDA) and the Smart phone or Mobile phone.
briefcase or pocket depending on their sizes. They run on rechargeable batteries and also use an adapter which allows them to be plugged into a power outlet to be recharged. Portable computers are essential for many workers like salespeople, agents and managers who may be off-sites and in remote locations but need computing and communications resources as they travel. Many students are also increasingly purchasing portable computers as their primary home computers. The types of portable computers that are about the size of a standard paper notebook are called Laptop or Notebook computers. They are fully functioning computers that open to reveal a screen and a keyboard. Another type of portable computer is the Tablet PC or simply Tablet which is contained in a touchscreen panel. Most Tablets are a little smaller and weigh less than the average laptop. Earlier Tablets required stylus but modern ones are operated by fingers and a stylus is an option. Handheld computers are also portable. They are about the size of a pocket calculator and have built-in keyboard or thumb pad. Some also accept input through digital pen or touch. Examples are the Personal Digital Assistant (PDA) and the Smart phone or Mobile phone.
Embedded Computers
Embedded computers are fixed into products designed to perform specific functions. Such products are mostly household appliances and cars. Embedded computers are put into household appliances and electronic devices like dishwashers, microwaves, washing machines and coffee makers in order to perform designated tasks. Electronic devices around the home like watches, answering machines, sewing machines, DVD players, television sets, pen, necklace and watch recorders and so forth, also make use of embedded computers. Cars also use embedded computers to assist with diagnosing faults, notifying the user of important conditions like under inflated tires, an oil filter that need changing, and controlling the use of airbag and other safety devices.
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