signature

signature, in music: see musical notation.

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(1) See digital signature.

(2) A pattern used for matching. Also called a "fingerprint" or "definition." For example, antivirus companies maintain a database that contains the virus code (the signature) of each of the known viruses. To detect a virus, the antivirus program looks for these code strings in executable programs. Spyware blockers that look for spyware and adware also use signature patterns.

An intrusion detection system also uses signatures, which are patterns that suggest an attack. For example, excessive logins that failed or the execution of certain programs.

(3) A unique number built into hardware or software for identification.

(4) A group of printed pages used in the construction of a book or booklet. Typically comprising 16 or 32 pages, signatures may also be 8, 12, 24, 48 or 64 pages long. The signature is printed on one large sheet of paper in a certain "imposition" order that, when cut and folded, results in the correct page sequence. The signatures are then bound together to make the final product.

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1.		signature - A set of function symbols with arities.
2.	(messaging)	signature - (Or sig) A few lines of information about the sender of an electronic mail message or news posting. 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.
3.	(programming)	signature - 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 <gb@cs.purdue.edu>. ftp://ftp.cs.purdue.edu/pub/gb/.