The development of electronic computers can be divided into five generations depending upon the technologies used. The following are the five generations of computers.

 

First Generation of Computers (1942-1955)

The beginning of commercial computer age is from UNIVAC (Universal Automatic Computer). It was developed by two scientists Mauchly and Echert at the Census Department of United States in 1947. The first generation computers were used during 1942-1955. They were based on vacuum tubes. Examples of first generation computers are ENIVAC and UNIVAC-1.

 

Second Generation Computers (1955-1964)

The second generation computers used transistors. The scientists at Bell laboratories developed transistor in 1947. These scientists include John Barden, William Brattain and William Shockley. The size of the computers was decreased by replacing vacuum tubes with transistors. The examples of second generation computers are IBM 7094 series, IBM 1400 series and CDC 164 etc.​

 

Third Generation Computers (1964-1975)

The Third generation computers used the integrated circuits (IC). Jack Kilby developed the concept of integrated circuit in 1958. It was an important invention in the computer field. The first IC was invented and used in 1961. The size of an IC is about ¼ square inch. A single IC chip may contain thousands of transistors. The computer became smaller in size, faster, more reliable and less expensive. The examples of third generation computers areIBM 370, IBM System/360, UNIVAC 1108 and UNIVAC AC 9000 etc.

 

Fourth Generation Computers (1975)

The fourth generation computers started with the invention of Microprocessor. The Microprocessor contains thousands of ICs. Ted Hoff produced the first microprocessor in 1971 for Intel. It was known as Intel 4004. The technology of integrated circuits improved rapidly. The LSI (Large Scale Integration) circuit and VLSI (Very Large Scale Integration) circuit was designed. It greatly reduced the size of computer. The size of modern Microprocessors is usually one square inch. It can contain millions of electronic circuits. The examples of fourth generation computers are Apple Macintosh & IBM PC.

 

Fifth Generation Computers (Present)​

The term "fifth generation" was intended to convey the system as being a leap beyond existing machines. In the history of computing hardware, computers using vacuum tubes were called the first generation; transistors and diodes, the second;integrated circuits, the third; and those using microprocessors, the fourth. Whereas previous computer generations had focused on increasing the number of logic elements in a single CPU, the fifth generation, it was widely believed at the time, would instead turn to massive numbers of CPUs for added performance.

 

Sixth Genration Computers(Present)

 The sixth generation of computer differs from previous generations in terms of size, processing speed and the complexity of tasks that computers can now perform. Back in the earliest stages of computing, computers contained vacuum tubes and magnetic drums. They were large, expensive and could only perform one task at a time. They were also prone to malfunctions and had the self-destructive inclination to overheat due to the vast amount of electricity it used and heat it generated.