Microcomputers (Personal computers)

Microcomputers are the most common type of computers in existence today, whether at work in school or on the desk at home. The term "microcomputer" was introduced with the advent of single chip microprocessors. The term "microcomputer" itself, is now practically an anachronism.

These computers include:

Desktop computers

Desktop means exactly that: a machine that is designed to sit on or under your desk.Desktop computers can be very convenient  in business or at home, and they are by far the best selling type of PCs in the world today.

Laptop and notebook computers

Usually these are  very powerful little boxes no bigger than a small briefcase. Now it is difficult to say what is better: a portable or a stationary computer. Comparison of both types demonstrates that  by functionality, the stationary and the portable  computers have  approximately the same useful scores.

Tablet PC

Tablet PC is a new step of development of portable computers.You can switch screen from a horizontal view to a vertical one, hold the tablet PC on your lap while you write notes on the screen or peck out words on its virtual keyboard with a digital pen.

Palmtop computers

A small computer that literally fits in your palm. Compared to full-size computers, palmtops are severely limited, but they are practical for certain functions such as phone books and calendars. Palmtops that use a pen rather than a keyboard for input

Personal digital assistants(PDA)

These are very small computers with

Programmable calculator

Programmable calculators allow the user to

limited  functionality. The general  function of such computers is  organizing.These  devices sometimes are named "handhelds". There is also a lot of entertainment value in the PDA.  You can find many games to please any taste, and.  use software to carry your pictures, listen to music, watch a movie.

write and store programs in the calculator in order to solve difficult problems or automate an elaborate procedure.

Minicomputers (Midrange computers)

A minicomputer (colloquially, mini) is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems (mainframe computers) and the smallest single-user systems (microcomputers or personal computers). The contemporary term for this class of system is midrange computer, such as the higher-end SPARC, POWER and Itanium -based systems from Sun Microsystems, IBM and Hewlett-Packard.

Mainframe Computers

The term mainframe computer was created to distinguish the traditional, large, institutional computer intended to service multiple users from the smaller, single user machines. These computers are capable of handling and processing very large amounts of data quickly. Mainframe computers are used in large institutions such as government, banks and large corporations. These institutions were early adopters of computer use, long before personal computers were available to individuals. "Mainframe" often refers to computers compatible with the computer architectures established in the 1960s. Thus, the origin of the architecture also affects the classification,not just processing power. The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently.

Classes by function

Servers

Server usually refer to a computer that is dedicated to providing a service. For example, a computer dedicated to a database may be called a "database server". "File servers" manage a large collection of computer files. "Web servers" process web pages and web applications. Many smaller servers are actually personal computers that have been dedicated to providing services for other computers.

Workstation

Workstations are computers that are intended to serve one user and may contain special hardware enhancements not found on a personal computer.

Embedded computers

Embedded computers are computers that are a part of a machine or device. Embedded computers generally execute a program that is stored in non-volatile memory and is only intended to operate a specific machine or device. Embedded computers are very common. Embedded computers are typically required to operate continuously without being reset or rebooted, and once employed in their task the software usually cannot be modified. An automobile may contain a number of embedded computers; however, a washing machine and a DVD player would contain only one. The central processing units (CPUs) used in embedded computers are often sufficient only for the computational requirements of the specific application and may be slower and less expensive than CPUs found in a personal computer.

Supercomputer

A supercomputer is focused on performing tasks involving intense numerical calculations such as weather forecasting, simulations or complex computations. The distinction between supercomputers and mainframes can be difficult to define at times. Supercomputers tend to focus on floating point performance. Mainframes, while providing a lot of processing power, focus more on data throughput and reliability, availability and serviceability (RAS), and generally perform many data handling operations involving minor computations.