Four generations of computers have evolved since the 1950s. Each generation reflected a change in hardware that was smaller in size but had greater capabilities to control computer operations. The first commercial computer was developed by John Eckert and John W. Mauchly in 1951 and was known as the Univac 1. For the next 25 years, mainframe computers were used to perform calculations in large businesses. Supercomputers have been used in science and engineering, to design airplanes and nuclear reactors, and to predict the world's weather patterns. Minicomputers appeared in the early 1980s in small businesses, manufacturing plants, and factories. Computers today are divided into four categories based on size, cost, and processing capacity. They are supercomputers, mainframes, minicomputers and microcomputers more commonly known as Personal Computers. Personal computers can be further divided into desktop, network, laptop, and handheld. In the 1970s, with the development of the Internet by the United States Department of Defense, the information age began