The first generation (roughly 1950–1959) is characterized by the emergence of commercial computers. During this time, computers were used only by professionals. They were locked in rooms with access limited only to the operator or computer specialist. Computers were bulky and used vacuum tubes as electronic switches. At this time, computers were affordable only by big organizations.

Second-generation computers (roughly 1959–1965) used transistors instead of vacuum tubes. This reduced the size of computers, as well as their cost, and made them affordable to small and medium-size corporations. Two high-level programming languages, FORTRAN and COBOL, were invented and made programming easier. These two languages separated the programming task from the computer operation task. A civil
engineer, for example could write a FORTRAN program to solve a problem without being involved in the electronic details of computer architecture.

Third generation
The invention of the integrated circuit (transistors, wiring, and other components on a single chip) reduced the cost and size of computers even further. Minicomputers appeared on the market. Canned programs, popularly known as software packages, became available. A small corporation could buy a package, for example for accounting, instead of writing its own program. A new industry, the software industry, was born. This generation lasted roughly from 1965 to 1975.

Fourth generation The fourth generation (approximately 1975–1985) saw the appearance of microcomputers. The first desktop calculator, the Altair 8800, became available in 1975. Advances in the electronics industry allowed whole computer subsystems to fit on a single circuit board.
This generation also saw the emergence of computer networks.

Fifth generation
This open-ended generation started in 1985. It has witnessed the appearance of laptop and palmtop computers, improvements in secondary storage media (CD-ROM, DVD, and so on), the use of multimedia, and the phenomenon of virtual reality.