File Extensions: File Extensions are a convention used in minicomputer systems as well as many microcomputer operating systems. They consist of a suffix to file names that indicates the file type and is often used to determine file handling. In the case of the common PC operating systems (other than Unix) the extensions are usually three letter tags. Thousands of extensions have been defined. The following is a short list of a few of the most common.

ExtensionFile Type
.ARC A compressed file in PKARC format
.BAT An MSDOS batch (command) file
.BMP A bitmap image file
.COM An MSDOS executable program in a specific core image format
.DLL A dynamic Link Library file
.DOC Usually a Microsoft Word file
.DXF Autocad file
.EPS An Encapsulated Postscript (printer) file
.EXE An executable program (several different formats)
.GIF An image file format
.GZ A Unix Compressed File
.HLP A Microsoft Help file
.HTM A Hypertext Markup language file
.HTT A hypertext Template file
.ICO An Icon file
.IDX A Data Base Index File
.INF A Script/Information file for Windows Setup
.INI A file containing program initialization information
.JPG A JPEG image file
.LZH A compressed file
.MPG An MPEG image file
.PCX An image file
.PCL A Hewlett Packard Print file
.PDF An Adobe Acrobat Document file
.PIF A Windows Program Interface File
.RTF A Rich Text Format Text file
.SYS An MSDOS executable program in a core image format used for device drivers.
.TIF An image file
.TXT An ASCII Text File
.WKx Various spreadsheet files (WKS, WK1, etc)
.WPx Various Word Perfect document files
.WMF Windows Metafile
.WRI A word processor file from WRITE (WIN3) or WORDPAD (WIN95)
.ZIP A compressed file in PKZIP format

The following two sites are only two of the many file extension lists available on the World Wide Web:

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