filename extension

The part of the filename following the period ( . ). It usually identifies the purpose of the file. An extension is limited to three characters. For example, form specification files have a .PER extension while compiled form files have a .FRM extension. 4GL source modules have a .4GL extension. INFORMIX-ESQL/C files have a .EC extension.

See also executable file, file, form specification file, help file, source file.