Computers are devices that are capable of performing series of Arithmetic and Logical operations. Computers are distinguished from a Calculating machine (such as an Electronic Calculator) by it's abbility to store computer programs (enabling to repeat its operations and logical decisions), by its number and complexity of the operations that it can perform, and it's abbility to process, store, and retrieve data without human intervention. Analog computers operate on data that is continuously varying; while Digital computers perform operations on discrete data.

Supercomputers very sophisticated machines that are designed to perform complex calculations at a maximum speed. Supercomputers are used to model very large dynamic systems, such as weather patterns.

Mainframes, the biggest and the most productive general-purpose systems, that are made to model large dynamic computing needs of a big organization that serves hundreds of terminals all at the same time.

Minicomputers are multi-user computers that are intended to meet the needs of a small company by serving up to hundreds of different terminals.

Microcomputers are computers that are powered by microprocessors. The microprocessors are subdivided into personal computers and workstations.

The advances in the technology of the integrated circuits have created the development of smaller and more powerful general-purpose digital computers. This has reduced the size of huge, multi-user mainframe computers, which in their beginning years were large enough to walk through to that of big pieces of furniture, but this has also made possible powerful, single-user personal computers and workstations that can sit on you desk! Because of the relatively low cost, these computers have largely replaced the old typewriters that most workplaces used to use.