FILENAME EXTENSION
\fˈa͡ɪlne͡ɪm ɛkstˈɛnʃən], \fˈaɪlneɪm ɛkstˈɛnʃən], \f_ˈaɪ_l_n_eɪ_m ɛ_k_s_t_ˈɛ_n_ʃ_ə_n]\
Definitions of FILENAME EXTENSION
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a string of characters beginning with a period and followed by one to three 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"
By Princeton University
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The portion of a filename, following thefinal point, which indicates the kind of data stored in thefile - the file type.Many operating systems use filename extensions, e.g. Unix,VMS, MS-DOS, Microsoft Windows. They are usually fromone to three letters (some sad old OSes support no more thanthree). Examples include "c" for C source code, "ps" forPostScript, "txt" for arbitrary text.NEXTSTEP and its descendants also use extensions ondirectories for a similar purpose.Apart from informing the user what type of content the fileholds, filename extensions are typically used to decide whichprogram to launch when a file is "run", e.g. bydouble-clicking it in a GUI file browser. They are alsoused by Unix's make to determine how to build one kind offile from another.Compare: MIME type.Tony Warr's comprehensive list(http://camalott.com/~rebma/filex.html).FAQS.org Graphics formats(http://faqs.org/faqs/graphics/fileformats-faq/).
By Denis Howe
