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Basic principles of computers

A computer receives individual pieces of data, changes the data into more useful information, and then tells the operator what the information is. For example, a person who wants to find the sum of four numbers enters them into the computer. In only a fraction of a second, signals that represent these numbers are changed into signals that represent the sum. The computer then displays the sum for the user. How a computer operates. People use input devices to enter data into computers. One of the most common input devices is the computer terminal, which looks like a typewriter keyboard combined with a television screen. Data that are typed on the keyboard appear on the screen. At the same time, the data go to the memory. The memory also stores a program--the step-by-step series of instructions for the computer to follow. The processor manipulates the data according to the program.

The processed information is sent to an output device, which presents it to the computer user. In many cases, the computer terminal that served as the input device also acts as the output device, and its screen displays the results. Printers are another important kind of output device. File storage devices are used to save information and programs for future use.

All data handled by computers, including words, enter the processor in the form of digits. Computers commonly use the digits of the binary numeration system (see NUMERATION SYSTEMS [The binary system]). Unlike the familiar decimal system, which uses 10 digits, the binary system uses only two digits: 0 and 1. These digits are called bits. Different combinations of bits represent letters, symbols, and decimal numerals. Each such combination of bits is called a byte. For example, according to one standard code, the binary representation for the letter A is 100 0001, while the binary representation for the letter Z is 101 1010. Each symbol and decimal numeral also is represented by a specific combination of 0's and 1's.

Each of a computer's thousands of tiny electronic circuits operates much like an ordinary light switch. When a circuit is off, it corresponds to the binary digit 0. When a circuit is on, it corresponds to the digit 1. Binary digits, like decimal numbers, can be added, subtracted, multiplied, and divided. Thus, a computer can perform all the basic arithmetic operations.

Computer hardware and software. The physical equipment that makes up a computer system is called hardware. Hardware includes input and output devices, file storage devices, the memory, and the processor. The input and output devices and the file storage devices are also known as peripheral equipment.

Computer software consists of the programs that a computer uses to perform a task. People can either create or purchase software. Computers have vast and varied capabilities because of the many different kinds of available software.

Kinds of computers (Next)