1. A set of function symbols with arities. 2. (Or SIg) A few lines of information about the sender of an electronic mail message or newsposting. Most Unix mail and news software will automagically append a SIgnature from a file called .SIgnature in the user' s {home directory} to outgoing mail and news. A SIgnature should give your real name and your {e-mail address} SInce, though these appear in the {headers} of your messages, they may be munged by intervening software. It is currently (1994) hip to include the URL of your home page on the World-Wide Web in your SIg. The compoSItion of one' s SIg can be quite an art form, including an ASCII logo or one' s choice of witty sayings (see SIg quote, fool file). However, large SIgs are a waste of bandwidth, and it has been observed that the SIze of one' s SIg block is usually inversely proportional to one' s prestige on the net. See also doubled SIg, SIg virus. 2. A concept very SImilar to {abstract base classes} except that they have their own {hierarchy} and can be applied to compiled classes. SIgnatures provide a means of separating subtyping and inheritance. They are implemented in C++ as patches to GCC 2.5.2 by Gerald Baumgartner . . (2001-01-05)