Extensions are important because they tell your computer what icon to use for the file, and what application can open the file. For example, the docextension tells your computer that the file is a Microsoft Word file.
If you want to open a MAC OS X file in Windows, you may need to add the extension to a MAC OS X file name so Windows can recognize it. For example, if you have a Word 6 MAC OS X document named letter that you want to open in Windows, you need to rename the file letter.doc so that Word in Windows will recognize and open the file.
The list below explains some of the common extensions.
| File Extension | File Type |
|---|---|
| .AIFF or .AIF | Audio Interchange File Format |
| .AU | Basic Audio |
| .AVI | Multimedia Audio/Video |
| .BAT | PC batch file |
| .BMP | Windows BitMap |
| .CLASS or .JAVA | Java files |
| .CSK | ClarisWorks for Windows |
| .CVS | Canvas |
| .DBF | dbase II, III, IV data |
| .DIF | Data Interchange format |
| .DOC | Microsoft Word for Windows/Word97 |
| .EPS | Encapsulated PostScript |
| .EXE | PC Application |
| .FM3 | Filemaker Pro databases (the numbers following represent the version #) |
| .GIF | Graphics Interchange Format |
| .HQX | Macintosh BinHex |
| .HTM or .HTML | Web page source text |
| .JPG or JPEG | JPEG graphic |
| .MAC | MacPaint |
| .MAP | Web page imagemap |
| .MDB | MS Access database |
| .MID or .MIDI | MIDI sound |
| .MOV or .QT | QuickTime Audio/Video |
| .MTB or .MTW | MiniTab |
| Acrobat -Portable document format | |
| .P65 .T65 |
PageMaker (the numbers following represent the version #) P=publication, T=template |
| .PNG | Public Network graphic |
| .PPT | PowerPoint |
| .PSD | Adobe PhotoShop |
| .PSP | PaintShop Pro |
| .QXD | QuarkXPress |
| .RA | RealAudio |
| .RTF | Rich Text Format |
| .SIT | Stuffit Compressed Archive |
| .TAR | UNIX TAR Compressed Archive |
| .TIF | TIFF graphic |
| .TXT | ASCII text (Mac text does not contain line feeds--use DOS Washer Utility to fix) |
| .WAV | Windows sound |
| .WK3 | Lotus 1-2-3 (the numbers following represent the version #) |
| .WKS | MS Works |
| WPD or .WP5 | WordPerfect (the numbers following represent the version #) |
| .XLS | Excel spreadsheet |
| .ZIP | PC Zip Compressed Archive |
