ASCII or American Standard Code for Information Interchange, a set of codes used to represent letters, numbers, a few symbols, and control characters. Originally designed for teletype operations, it has found wide application in computers. A seven-digit (or seven-bit) binary number (see binary system) can represent one of 128 distinct codes. Thus, in decimal equivalents, the series 72, 69, 76, 76, 79 represents the letters h, e, l, l, o in ASCII. With the introduction of its personal computer in 1981, the International Business Machines Company (IBM) increased the number of available characters to 256 by using an eight-bit byte. This IBM-extended ASCII set has become a de facto standard. However, the inability of US-ASCII to correctly represent many other languages became an obvious and intolerable misfeature as computer use outside the United States and United Kingdom increased. As a consequence, national extensions to US-ASCII were developed that were incompatible with one another. This in turn led to the standardization of 16-bit (or double-byte) and 32-byte character sets, such as Unicode, that could accommodate large numbers of linguistic and other symbols.

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