1. [syn: extension, filename extension, file name extension]
WordNet (r) 3.0 (2006):
n 1: a string of characters beginning with a period and followed
by one or more letters; the optional second part of a PC
computer filename; "most applications provide extensions
for the files they create"; "most BASIC files use the
filename extension .BAS" [syn: extension, filename
extension, file name extension]
The Free On-line Dictionary of Computing (30 December 2018):
The portion of a filename, following the
final point, which indicates the kind of data stored in the
file - the file type.
Many operating systems use filename extensions, e.g. Unix,
VMS, MS-DOS, Microsoft Windows. They are usually from
one to three letters (some sad old OSes support no more than
three). Examples include "c" for C source code, "ps" for
PostScript, "txt" for arbitrary text.
NEXTSTEP and its descendants also use extensions on
directories for a similar purpose.
Apart from informing the user what type of content the file
holds, filename extensions are typically used to decide which
program to launch when a file is "run", e.g. by
double-clicking it in a GUI file browser. They are also
used by Unix's make to determine how to build one kind of
file from another.
Compare: MIME type.
Tony Warr's comprehensive list
FAQS.org Graphics formats