The move from World War II to the present can be divided into roughly four generations:

First Generation (1951 to 1958)

Highlights: Vacuum tubes, UNIVAC computer

Running from roughly 1951 through 1958, generation one computers are characterized by their use of vacuum tubes.

The standout of the era is the UNIVAC (UNIVersal Automatic Computer) which was the first true general purpose computer in America designed for both alphabetic as well as numeric uses. This made the UNIVAC a standard for business, not just science and the military.

Punched cards formed the input to the machines and all programming was done in machine language (i.e., numbers that were interpreted by the machine as commands.

UNIVAC Installation Anecdote

Second Generation (1959 to 1964)

Highlights: Transistors, Higher order languages

The transistor dominated computers during the period 1959 to 1964. Computers became smaller.

There were no outstanding computers during this period, however it was famous for development of higher order languages. Computers could now be programmed with English-like commands instead of strings of numbers. Programming efficiency improved greatly.

FORTRAN for scientists and COBOL for business were the two major languages of the era.

Brief History of FORTRAN

Grace Hopper Wit and Wisdom

Third Generation (1965 to 1970)

Highlights: Integrated circuits, IBM 360 and minicomputers

1965 to 1970 saw the introduction of the integrated circuit. Instead of large boards, circuits were developed on single chips of silicon. Two devices stand out during this period:

IBM introduced its 360 series mainframe computers and the smaller minicomputer made their debut. Equivalent to a larger computer, but with smaller memory and slower processing, the minicomputer made computers available to the smaller businesses.

IBM History

Fourth Generation (1971 to present)

Highlights: Microprocessors, Personal computers

Microprocessors derived from integrated circuits and this put computers on the office desk. Generally thought to begin in 1971 and run to the present, generation four features the microprocessor and derivative personal computer.

The computers of the fourth generation are roughly 100 times smaller than those of generation one, yet they are at least as powerful, if not more so.

Microcomputer History