Digital Technology, study and development of devices that store and manipulate numbers. Digital devices can translate words and pictures into numbers for a computer to process and then translate the numbers back into pictures or words. By contrast, analogue technology is the study of devices that function without storing or using numbers. For example, an analogue watch contains a complex mechanism of gears that produce the steady motion of its hands (see Analogue Display). Although numbers may be painted on to the face of the watch, the mechanism does not store or use those numbers to keep time. Inside a digital watch, electronic circuitry stores and manipulates numbers representing the time, and these are displayed on the face of the watch. Use of the Binary System Across the world, people generally represent numbers using the decimal system, writing numbers using ten digits, 0 to 9, and combinations of these digits. Every digit in a decimal number represents powers of ten. Modern digital devices store numbers using only two digits, 1 and 0, called bits. Such numbers are called binary numbers (see Number Systems; Base (mathematics). Every digit in a binary number represents a power of two. For example, in the binary number 101, the 1 at the right represents 1 x 20; the 0 in the middle represents 0 x 21; and the 1 to the far left represents 1 x 22. The decimal equivalent of 101 is (1 x 22) + (0 x 21) + (1 x 20) = 4 + 0 + 1 = 5. Processing Digital Information Digital devices such as computers have electronic circuits that can turn on and off extremely rapidly. When a circuit is on, it represents a value of 1, and when a circuit is off, it represents a value of 0 in the binary number system. Digital devices perform mathematical operations by turning these switches on and off according to the rules of binary arithmetic. The simplicity of binary arithmetic, combined with the rapid rate at which a computer can manipulate binary data, makes binary numbers ideally suited for computers. All instructions that direct the function of computers and all data manipulated by computers are first converted into binary numbers so they may be processed more efficiently and more quickly. Digital devices are designed to perform mathematical operations as fast as possible. Devices that perform parallel processing complete multiple operations simultaneously. Pipelined devices behave like an assembly line, so that at any given time, several operations in various stages are being executed on different data. Computers translate information from the user into binary numbers in a process called digital encoding. Letters can be encoded by replacing every letter with its numerical position (1-26) in the alphabet, and then converting these decimal numbers into binary equivalents. A sound can be encoded as a series of numbers that measure its pitch and volume at each instant in time. An image can be encoded as a sequence of numbers that represent the colour and brightness of each portion of the picture. The computer is able to decode information by converting the numbers back into letters, sounds, or images. Digital devices can process encoded information in a variety of useful ways. They can sharpen blurry images, clarify sounds, and check the spelling of words by manipulating the numbers representing information. A digital device can also compress information by identifying a recurring sequence of numbers and then representing that sequence with a single number. Compression saves space when storing the information, and it saves time when transferring the information from computer to computer. Progress in digital technology is driven by the need for rapid and effective communication of increasing amounts of data. Advanced compression technologies allow computers to find, store, and transmit massive amounts of information efficiently. Digitally encoded text, sounds, images, and video can be stored together on magnetic media and compact discs and broadcast over cable to homes (see Cable Television) and over satellites to cellular telephones (see Cellular Radio).