The History of Computer DevelopmentThe rapidly advancing field of electronics led to construction of the first general-purpose electronic computer in 1946 at the University of Pennsylvania. It was Electronic Numerical Integrator And Computer or ENIAC, the device contained 18,000 vacuum tubes and had a speed of several hundred multiplications per minute. Its program was wired into the processor and had to be manually altered.Later transistors appeared. The use of the transistor in computers began in the late 1950s. It marked the advent of smaller, faster elements than it was possible to create with the use of vacuum-tube machines. Because transistors use less power and have a much longer life, computers alone were improved a lot. They were called second-generation computers.Components became smaller and the system became less expensive to build.Modern digital computers are all conceptually similar, regardless of size and shape. Nevertheless, they can be divided into several categories on the basis of cost and performance.The first one is the personal computer or microcomputer, a relatively low-cost machine, usually of desk-top size. Sometimes they are called laptops. They are small enough to fit in a briefcase. The second is the workstation, a microcomputer with enhanced graphics and communications capabilities that make it especially useful for office work. And the server computers, a large expensive machine with the capability of serving the needs of major business enterprises, government departments, scientific research establishments. The largest and fastest of these are called supercomputers.A digital computer is not actually a single machine, in the sense that most people think of computers. Instead it is a system composed of five distinct elements: a central processing unit, input devices, memory storage devices, output devices and a communications network, called a «bus» that links all the elements of the system and connects the system itself to the external world.
