is simply an unvarying rule for replacing a piece of information (e.g., letter, word, or phrase) with another object, but not necessarily of the same sort. Probably the most widely known CodE
in use today is the American Standard Code for Information Interchange (ASCII). Employed in all personal computers and terminals, it represents 128 characters (and operations such as back space and carriage return) in the form of seven-bit binary numbers--i.e., as a string of seven 1s and 0s. In ASCII a lowercase a is always 1100001, an uppercase A always 1000001, and so on. In the first quarter of this century, before the telegraph was supplanted by radio communications, elaborate commercial codes that encoded complete phrases into single words (five-letter groups) were developed, so that telegraphers became conversant with such "words" as BYOXO (Are you trying to crawl out of it?), LIOUY (Why do you not answer my question[s]?), AYYLU (not clearly coded, repeat more clearly), or AZQUL (recheck coding and verify). Acronyms are also widely known and used codes, as, for example, RSVP and WASP. Occasionally a code word achieves an independent existence (and meaning) while the original equivalent phrase is forgotten or at least no longer has the precise meaning attributed to the code word--e.g., SNAFU.