History of COMPUTERS

Computer is a machine that performs calculations and processes information with astonishing speed and precision. A computer can handle vast amounts of information and solve complicated problems. It can take thousands of individual pieces of data and turn them into more usable information--with blinding speed and almost unfailing accuracy. The most powerful computers can perform billions of calculations per second.

Computers have changed the way people work. They handle many tasks in business, education, manufacturing, transportation, and other fields. Many tedious tasks performed by large numbers of clerical workers are now done by computers. They provide scientists and other researchers with a clearer understanding of nature. They give people who work with words an effective way to create documents. They enable designers and artists to see things that have never been seen before. Computers produce new information so quickly and accurately that they are changing people's views of the world. People can access large electronic databases remotely. For these and other reasons, the computer is one of the most interesting and important machines ever invented.

The most common type of computer, by far, is the digital computer. Digital means having to do with numbers. Digital computers perform tasks by changing one set of numbers into another set. All data--numerals, pictures, sounds, symbols, and words--are translated into numbers inside the computer. Everything a digital computer can do is based on its ability to perform simple procedures on numbers--such as adding, subtracting, or comparing two numbers to see which is larger. Digital computers are so widespread that the word computer alone almost always refers to a digital computer. The largest digital computers are parts of computer systems that fill a large room. The smallest digital computers--some so tiny they can pass through the eye of a needle--are found inside wristwatches, pocket calculators, and other devices.

All digital computers have two basic parts--a memory and a processor. The memory receives data and holds them until needed. The memory is made up of a huge collection of switches. The processor changes data into useful information by converting numbers into other numbers. It reads numbers from the memory, performs basic arithmetic calculations such as addition or subtraction, and puts the answer back into the memory. The processor performs this activity over and over until the desired result is achieved. Both the memory and the processor are electronic--that is, they work by sending electrical signals through wires.

The smallest digital computers consist only of the memory and the processor. But larger digital computers are part of systems that also contain input equipment and output equipment. The operator uses an input device, such as a keyboard, to enter instructions and data into the computer. After processing is complete, an output device translates the processed data into a form understandable to the user--words or pictures, for example. Typical output devices include printers and visual displays that resemble television screens.

People can think about problems and figure out how to solve them. But computers cannot think. A person must tell the computer in very simple terms exactly what to do with the data it receives. A list of instructions for a computer to follow is called a program.

People have used calculating devices since ancient times. The first electronic digital computer, built in 1946, filled a huge room. Since then, rapid improvements in computer technology have led to the development of smaller, more powerful, and less expensive computers.

In addition to digital computers, there are two other general types of computers: analog computers and hybrid computers. Analog computers work directly with a physical quantity, such as weight or speed, rather than with digits that represent the quantity. Such computers solve problems by measuring a quantity, such as temperature, in terms of another quantity, such as the length of a thin line of liquid in a thermometer. Hybrid computers combine the features of analog and digital computers. They have many of the same kinds of parts as an analog computer. But like digital computers, they process data by manipulating numbers. This article focuses on digital computers. For information on analog computers, see ANALOG COMPUTER.

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