File Extension

A (typically) three-character addition to a computer file name. With some computer platforms (in particular, DOS), the name of a file is limited to eight characters, followed by a period and a three-character extension (such as "FILENAME.EXT"). The extension is often used to indicate the file format in which the file was saved. Some common extensions used for graphics files include ".eps" (encapsulated PostScript), ".pct" (PICT), ".tif" (TIFF), etc. File extensions are useful means of indicating and determining file type. Also known as a file-name extension.

Many common file extensions used in DOS, Windows, and OS/2 include:

AIAdobe Illustrator

AIFAudio Interchange File Format

BAKBackup copy of an edited file

BMPBitmap graphic

CDRCorel Draw vector graphics

CMDOS/2 command file

COMDOS command file

DOCASCII text document

DLLDynamic link library

EPSEncapsulated PostScript file

EXEExecutable file, or machine language file

GIFGraphics Interchange Format file

HLPHelp file


INIInitialization file




PCXZsoft bitmap file

PDFPortable Document Format file

PIFProgram Information File

PSPostScript file

SEAStuffIt self-expanding archive

SITStuffIt (compressed) archive)

SYSOperating system component

TEXTEX or LATEX document

TGATARGA graphics file

TIFTIFF graphics file

TMPTemporary file

TXTASCII text file

WAVSound wave file

WKQQuattro spreadsheet file

WMFWindows MetaFile

WKSLotus 1-2-3 worksheet file

XLSMicrosoft Excel worksheet file

ZIPPKZIP-compressed file

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