In the field of computing, information can be conveyed in digital or analog formats. Continuity is the differentiating factor between the two. For example, digital devices are only able to display information in finite units (10 degrees versus 10.0625 degrees), while analog devices display information that corresponds more precisely to real world phenomena. Digital watches display time in measured increments while analog watches show time unfold continuously through the circular movement of mechanical hands.
Although analog computers are used for simulating real-word conditions in a variety of fields, including nuclear power and electronics, the majority of computers, including those used for e-commerce, are digital machines. They process information in a binary format of zeroes and ones (0, 1, 10, 11, 100, 111, and so on). Accordingly, while the software programs used during e-commerce—including Web browsers and database programs—are written in high-level programming languages like C++ and Java that closely resemble human grammar, they eventually are converted to commands consisting of ones and zeroes that a computer's hardware can accept and understand. Digital computers function through four essential components: an input-output device; a control unit; main memory; and an arithmetic-logic unit.
The difference between analog and digital information can be shown in the audio recording process. Analog devices record sound waves directly onto magnetic tape, whereas digital devices take the same wave, convert it to a sequence of ones and zeroes, and store it for future use. When played back, the numbers are converted into electronic signals resembling the original sound wave. Digital information, including computer software programs, word processing documents, digital audio, and digital video, can be duplicated an infinite number of times without a loss in quality or integrity; the numeric expressions of zeroes and ones remain the same throughout time. In comparison, the quality of analog information, such as songs recorded on magnetic tape, deteriorates with successive generations as copies are made.
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SEE ALSO: Analog
analog-to-digital conversion, the process of changing continuously varying data, such as voltage, current, or shaft rotation, into discrete digital quantities that represent the magnitude of the data compared to a standard or reference at the moment the conversion is made. There are two types of converters: electromechanical—also called shaft- or position-to-digital—and electronic. The most common use is to change analog signals into a form that can be manipulated by a digital computer, as in data communications; a modem, or data set, is a device that converts the digital signals produced by computers and terminals into analog signals that telephone circuits are designed to carry and then back to digital signals at the other end of the communication link. Similarly, in digital sound recording, audio signals are transformed into digital data, which are then recorded on a magnetic or optical disk or tape; the digitized data on the recording medium then must be changed back into the analog sound signals that can be used by a stereophonic sound system. See also digital-to-analog conversion.
See M. J. Demler, High-Speed Analog-to-Digital Conversion (1991); K. M. Daugherty, Analog-to-Digital Conversion: A Practical Approach (1995).
dig·it·al / ˈdijitl/ • adj. 1. relating to or using signals or information represented by discrete values (digits) of a physical quantity, such as voltage or magnetic polarization, to represent arithmetic numbers or approximations to numbers from a continuum or logical expressions and variables: digital TV. Often contrasted with analog. ∎ (of a clock or watch) showing the time by means of displayed digits rather than hands or a pointer. 2. of or relating to a finger or fingers. DERIVATIVES: dig·it·al·ly adv.
1. relating to a finger or toe.
2. relating to or designating information that can be represented by a series of numbers. d. hearing aid see hearing aid. d. image an electronically produced image, such as an image produced by digital radiography, made up of pixels, each of which has numbers to represent its position and shade. See digitization. d. radiography see radiography. d. subtraction a radiological technique that enhances X-ray images, most commonly of blood vessels, in which a digitized image taken before addition of the contrast medium is subtracted by computer from the images taken after contrast injection.
1. To translate graphical information into a series of numbers suitable for processing by (digital) computer. For example, topographic detail can be taken from a map and digitized to produce a computer-generated topographic cross-section. The superimposition of an orthogonal coordinate system on to an image and the recording of the data in a machine-readable form assumes that a two-dimensional image is being analysed. It can be done three-dimensionally if stereophotographs are analysed. Fully automated systems also exist for this type of work.
2. To convert analog data into digital form by sampling the continuous record at discrete sample intervals. See also ALIASING; and SAMPLING FREQUENCY.
dig·i·tize / ˈdijiˌtīz/ • v. [tr.] [usu. as adj.] (digitized) convert (pictures or sound) into a digital form that can be processed by a computer. DERIVATIVES: dig·i·ti·za·tion / ˌdijitəˈzāshən/ n. dig·i·tiz·er n.