These extensions at the end of a filename refer to the type of file it is. This information is used by your operating system to launch an appropriate program when you click on the filename. Example: file.txt is a text file and can be opened by a text editor program.

.$$$ Temporary file .2GR A file that allows Windows to display text and graphics in standard mode on a 286 or 386 computer (filename extension). .386 Swap file; enables computer running in enhanced mode to use Windows with virtual memory (filename extension). .3GR A file that allows Windows to display text and graphics in enhanced mode on a 386, 486, or Pentium computer (filename extension). .906 Calcomp plotter .A3W MacroMedia Authorware Windows 3.5 (filename extension). .ABK AutoBackup, Corel Draw (filename extension). .ABR Brush - Adobe Photoshop (filename extension). .ACL Keyboard accelerator, Corel Draw 6 (filename extension). .ACM Windows system directory file (filename extension). .ACV Drivers for compressing or decompressing audio files, OS/2 (filename extension). .AD After Dark .ADB 1. Appointment DataBase, HP 100LX (filename extension). 2. Body file type, Ada language (filename extension). .ADD Adapter Driver - OS/2 (filename extension). .ADM AfterDark MultiModule (filename extension). .ADR AfterDark Randomizer (filename extension). AfterDark is a screensaver program that can be set to randomly display a variety of screensaver patterns one after another. .ADS Specification file type, Ada language (filename extension). .AFM Adobe Font Metrics - Type 1 font metrics (filename extension). .AG4 Access G4 .AI Adobe Illustrator .AIF Audio Interchange File Format or AIFF (filename extension). A format developed by Apple Computer for storing high-quality sampled audio and musical instrument information. It can be played on PC and Mac. .aiff Audio Interchange File Format. An uncompressed sound format developed by Apple Computer for storing high-quality sampled audio and musical instrument information. It can be played on PC and Mac, using QuickTime or Sound Player. .ALL Arts and Letters Library (filename extension). .ANI Animated cursor (filename extension). .ANS ANSI text (filename extension). .API Application Program Interface (filename extension). An interface between the operating system and application programs. .APP MacroMedia Authorware package (filename extension). .ARC ARC or ARC+ compressed .arj A PC compressed format found on European sites (filename extension), which can be decoded with unArjMac, DeArj, and SITEX10.EXE (win). .ART An art file, in some draw or paint applications (filename extension). .ASC ASCII text file .ASF Active Streaming File - HoTMetaL Pro (filename extension). .ASM Assembly Source Code .ASP Active Server Page - Microsoft (filename extension). .AST Assistant file - Claris Works (filename extension). Assistants guide the user through a task by asking a series of questions and then use the answers to perform a task. Assistants in Claris Works can be used to create such useful items as calendars, newsletters, stationery, labels, and address lists, to make footnotes within a file, to find documents, etc. .ATT AT&T .AU A sound file format used on Sun Microsystems or other UNIX computers .AVI AVI movie format .AVS Intel video capture format (filename extension). .b64 Base 64 (filename extension), the encoding format used by the Multipurpose Internet Mail Extension. .BAK Backup copy in DOS or OS/2 .BAS BASIC program file .BAT Batch .BFC Briefcase document - Windows 95 (filename extension). .BG Backgammon game (filename extension). .BI Binary file (filename extension). .BIN Driver .bin A MacBinary II encoded file (filename extension). This file type, downloaded as MacBinary or Binary, can be decompressed with Stuffit Expander.. .BK Backup copy .BK$ Backup file (filename extension). .BLT Wordperfect for DOS (filename extension). .BMP Bitmap .BNK Sim City game file (filename extension). .BRX Browse Index (filename extension). Found on multimedia CD-ROMs. .BTM Batch file - Norton Utilities (filename extension). .C C program file .CAB Microsoft compressed format .CAL Calendar or CALS .CAP Caption .CBT Computer-Based Training; a tutorial file (filename extension). .CCH Corel chart (filename extension). .CCM Lotus cc:Mail (filename extension). .CDA CD Audio track (filename extension). .CDR CorelDraw .CDT Corel Draw template (filename extension). .CDX Corel Draw compressed file (file extension). .CDX Visual FoxPro database index (filename extension). .CFB Compton’s multimedia encyclopedia (filename extension). .CFG Configuration .CFL Corel Flow (filename extension). .CGI Common Gateway Interface (filename extension). A file that makes it possible for HTTP servers to interface with computer programs to provide interactive functions like fill-out forms. .CGM CGM graphics .CHK Checkdisk - DOS .CHP Chapter - Ventura .CIF Chapter Information - Venture .CIM Sim City file (filename extension). .CIT Intergraph scanned image .CLP Clipboard .CMD Command file -- OS/2 .CMF Corel MetaFile (filename extension). .CMF SoundBlaster file (filename extension). .CMP LEAD Technologies graphics .CMV Corel Move animation (filename extension). .CNF Configuration file (filename extension). .CNQ Compuworks Design Shop (filename extension). .COB COBOL source code .COM Command file - small version of .EXE .CPE Fax Cover document (filename extension). .CPI Code Page - DOS .CPL Control Panel - Windows .CPP C++ program file .CPR Knowledge Access graphics .CPT Compact Pro .CPX Corel Presentation Exchange compressed file (filename extension). .CRD Windows Cardfile (filename extension). .CSC Corel Script (filename extension). .CSS Cascading Style Sheet (filename extension). .CSV Comma delimited .CTL Control file (filename extension). .CTY City file - SimCity (filename extension). .CUR Windows cursor image .CUT Dr. Halo graphics .CV Microsoft CodeView (filename extension). .CWK Claris Works (filename extension). .CWS Claris Works template (filename extension). .DAT Data .DB Table - Paradox .DBC Visual FoxPro database (filename extension). .DBF Database File - dBASE .DBT Database text - dBASE .DBX DATABEAM graphics .DCA IBM text .DCS Color Separation - EPS .DCT Dictionary .DD Disk Doubler .DDI Disk Doubler Image (filename extension). .DEF Definition - C++ (filename extension). .DER Certificate (filename extension). .DEV Device driver file (filename extension). .DG Autotrol graphics .DGN Intergraph graphics .DIB DIB graphics - Windows .DIC Dictionary .DIF Data Interchange Format spreadsheet .DLL Dynamic link library .DOC Document file .DOT Document Template - Microsoft Word (filename extension). .DOX MultiMate document .DPI Dots Per Inch - graphics .DPR Delphi project file (filename extension). .DRV Driver .DRW Designer graphics .DS4 Designer graphics, version 4 .DSF Designer graphics, version 6 .DWG AutoCAD vector format .DWG Drawing - AutoCAD (filename extension). .DX Document Imaging .DXF AutoCAD vector format .ED5 EDMICS graphics .EMF Enhanced Windows Metafile (filename extension). .eml electronic mail .enc encoded .EPS Encapsulated PostScript format .ESI Esri plot file .EXE Executable file -- machine code .FAX Fax .FDX Force Index .FH3 Aldus Freehand 3 (filename extension). .FLC AutoDesk animation .FLD Thumbnail folder - Hijaak .FLI AutoDesk animation .FLR Live3D (filename extension). .FLT Filter - graphics conversion .FM Framemaker (filename extension). .FM3 Format for 1-2-3 Version 3 .FMT Format - dBASE .FNT Font .FOG Fontographer font (filename extension). .FON 1. Bitmapped Font - Windows 2. Phone .FOR FORTRAN .FOT Windows TrueType font .FOX FoxBase .FP Claris FileMaker Pro (filename extension). .FP1 Flying Pigs (filename extension). .FP3 Filemaker Pro 3 .FPX FlashPix bitmap (filename extension). .FRM Form design -- Visual Basic .FRS WordPerfect Graphics Driver .G4 GTX RasterCAD .GCA GOCA graphics .GED Arts & Letters graphics .GEM GEM graphics .GEO VideoScope (filename extension). .GIF Graphics Interchange Format .GLY Glossary .GP3 CCITT compressed Group 3 TIFF file (filename extension). .GP4 Group 4 - CALS, ITU (filename extension). CCITT compressed Group 4 TIFF file. .GRA Microsoft Graph (filename extension). .GRF Graph .GRP Group .GX1 Show Partner graphics .GX2 Show Partner graphics .GZ GNU gzip compressed file - Unix .H Header (filename extension -- C). .HDF Hierarchical Data File .HED HighEdit document (filename extension). .HEL Microsoft Hellbender game file (filename extension). .HGL HP Graphics Language (filename extension). .HLP Help .HPJ Help Project - Visual Basic (filename extension). .HPL HP Graphics .HQX BinHex (filename extension -- Macintosh). .HST Host .HT HyperTerminal (filename extension). .htm DOS filename extension for a document with HTML coding, which can be read by WWW browsers. .html Filename extension for a document with HTML coding, which can be read by WWW browsers. .HWP Hangul Word Processor (filename extension). .HYC Hyphenation - WordPerfect .HYP Hyphenation .ICA IOCA graphics .ICB Targa bitmap (filename extension). .ICM Image Colour Matching (filename extension). .ICO Icon - Windows or OS/2 .ICON Sun icon and cursor .IDD Instrument Definition - MIDI (filename extension). .IDE Integrated Development Environment configuration (filename extension) .IDX Index .IFF Amiga .IGF Inset Systems graphics - Hijaak .IIF Interchange File - QuickBooks for Windows (filename extension). .IL Icon Library .ima Winimage compressed format These files can be decoded or mounted by ShrinkWrap. .image Mac disk image (filename extension); a compressed format which can be decoded or mounted by DiskCopy, Disk Image Mounter, Disk Charmer, and ShrinkWrap (ImageMaster). .IMG Image. This file is a Macintosh Disk Image. Disk Copy can be used to mount the disk image on the Macintosh desktop. The mounted disk image will behave like a read-only disk. .IND Index .INF Information .INI Initialization - configuration settings .IOB Imagine file (filename extension). .ISU Netscape file (filename extension). .IT MOD music file format (filename extension). .IW Idlewild screensaver (filename extension). .IX Index File - Framemaker (filename extension). .JFF or .JFIF JPEG File Interchange Format; a 24-bit graphic format. It can be opened with QuickTime, a WWW browser, or a graphics viewer such as JPEGView. .JIF JPEG Image Format (filename extension). .JPEG JPEG bitmap (filename extension). .JPG file extension for JPEG (Joint Photographic Experts Group). A file stored in JPEG format. JPEG,an ISO/ITU standard for storing images with high compression capability, uses a discreet cosine transform that can achieve compression rates of 100:1 (significant loss of data from original) and 20:1 (minimal loss). C-Cube Microsystems introduced the first JPEG chip. .JT JT Fax .JTF JPEG bitmap (filename extension). .KDC Kodak Photo-Enhancer (filename extension). .KFX Kofax .LBL Label - dBASE .LBM Deluxe Paint graphics file .LDB Lock file - Microsoft Access (filename extension). .LEG Legacy document (filename extension). .lha Filename extension for a PC/Amiga compression format decodable by LHA Expander or MacLHA. .lhs Literate Haskell source file .lhz LHA compression file .LIB Library .LIC License file - shareware (filename extension). .LOG Log .LST List (filename extension). .LWP Lotus Word Pro document (filename extension). .LZH LHARC compression .lzs PC/Amiga compression format .M3D Motion 3D - Corel (filename extension). .MAC MacPaint .MAF Microsoft Access Form (filename extension). .MAK Makefile .MAM Microsoft Access Macro (filename extension). .MAP Map - linkage editor .MAQ Microsoft Access Query (filename extension). .MAR Microsoft Access Report (filename extension). .MAT Microsoft Access Table (filename extension). .MCS MathCAD format .MCW Microsoft Word for Macintosh (filename extension). .MDB Access database .MDX Multi-index .MET Metafile - OS/2 .MEU Menu .MFF MIDI File Format (filename extension). .MGF Micrografx Draw Font (filename extension). .MI Miscellaneous (filename extension). .MIC Microsoft Image Composer (filename extension). .MID MIDI

.MIFF An ImageMagick file format .MIL Group 4 .mime MIME (filename extension); the encoding format used by the Multipurpose Internet Mail Extension. .MME Mime encoded file (filename extension); the encoding format used by the Multipurpose Internet Mail Extension. .MMF Microsoft Mail File (filename extension). .MMM Macromind animation .MOD (For module). A music file format that contains digitized sound samples A .MOD file takes more memory than a MIDI file because a MIDI file contains instructions for making sounds but not the actual sound samples. There are .MOD players for Amiga, PC, and Macintosh computers. .moov QuickTime movie. This file can be viewed with QuickTime Player. .MOV Movie - QuickTime .movie QuickTime movie. This file can be viewed with QuickTime Player. .MOZ Mozilla - Netscape cache file (filename extension). .mp2 MPEG Layer II compressed audio. This file can be played using QuickTime Player and some other sound players. .mp3 MPEG Layer III compressed audio. This file can be played with QuickTime Player, Real Player, and some other sound players. .MPE MPEG (filename extension). .MPEG MPEG movie or animation file. This file can be played with QuickTime Player. .MPG MPEG encoded file. This file is an MPEG movie, and can be played with QuickTime Player. .MPNT Macintosh MacPaint .MPP Microsoft Project project file (filename extension). .MPT Microsoft Project template file (filename extension). .MPX Microsoft Project export file (filename extension). .MRK Markup - Informative Graphics .MSG Message file .MSN Microsoft Network document (filename extension). .MSP Microsoft Paint .MUS Music (filename extension). .MVB Microsoft Multimedia Viewer (filename extension). .MYS Myst saved game file (filename extension). .NDX Index - dBASE .NET Network file (filename extension). .NG Norton Guides .NLM NLM program - NetWare .NTF Notes Template File - Lotus Notes database (filename extension). .OAB Outlook Address Book - Microsoft (filename extension). .OAZ OAZ Fax .OBD Microsoft Office Binder (filename extension). .OBJ Object module .OCX Object Linking and Embedding (OLE) Custom Control (filename extension). .OLB OLE Object Library (filename extension). .OLE OLE object (filename extension). .ONX Onyx Graphics Postershop (filename extension). .ORI Original .OVL Overlay module .OVR Overlay module .OZM Sharp Organizer memo bank .OZP Sharp Organizer telephone bank .P10 Tektronix Plot10 .PAB Personal Address Book - Microsoft (filename extension). .PAK Quake game data (filename extension). .PAL Paintbrush palette (filename extension). .PAS Pascal program file .PAT Pattern - Corel Draw (filename extension). .PBK Microsoft Phonebook (filename extension). .PBM Portable Bit Map .PCD Photo CD format .PCL HP LaserJet .PCM LaserJet cartridge information .PCS PICS animation (filename extension). .PCT PC Paint .PCW PC Write .PCX 1. PC Paintbrush 2. Graphics file - Zsoft format .PDG PrintShop Deluxe (filename extension). .PDV PC Paintbrush printer driver .PFA Type 1 font - ASCII .PFB Type 1 font - encrypted .PFM Postscript Font Metrics; Windows Type 1 font metrics .PGL HPGL 7475A plotter - vector graphics .PGM Portable Gray Map bitmap (filename extension). .PHTML HTML document with preprocessing instructions (PPIs) (filename extension). .PIC PICT graphics format, or PIXAR picture file .PICT Macintosh QuickDraw/PICT This kind of file stores images in QuickDraw vector format. PICT2 can have grayscale bitmapped images also. .PIF Program Information File - Windows .PIT PackIt - Macintosh compression .PIX Inset Systems graphics .PJX Project file - Visual FoxPro (filename extension). .pkg AppleLink package compression format These files are decodable by StuffIt Expander. .PL Perl script (filename extension). .PLT Plotter drawing (filename extension). .PM PageMaker .PM3 PageMaker 3 document .PM4 PageMaker 4 document .PM5 PageMaker 5 document .PNG 1. Portable Network Graphics bitmap (filename extension). 2. Paint Shop Pro Browser (filename extension). .POV Persistence Of Vision raytracer (filename extension). .PPA PowerPoint Add-in - Microsoft (filename extension). .PPD PostScript Printer Description .PPM Portable PixelMap (filename extension). .PPS PowerPoint Slideshow (filename extension). .PPT PowerPoint presentation (filename extension). .PRD Printer driver - Microsoft Word, Word Perfect, Microsoft Works (filename extension). .PRG A dBASE source code file .PRJ Project file .PRN 1. Print file - temporary 2. XyWrite printer driver 3. PostScript file .PRS WordPerfect printer driver .PRT Formatted text .PS PostScript. This is a plain text file. .PSD Photoshop Document .PUB Publication - Ventura Publisher, Microsoft Publisher (filename extension). .PWD Pocket Word document - Microsoft (filename extension). .PWZ Microsoft PowerPoint Wizard (filename extension). .PXL Microsoft Pocket Excel (filename extension). .QBW QuickBooks for Windows (filename extension). .QDK Quarterdeck Qemm (filename extension). .QLB Quick Library (filename extension). .QLC ATM font information .QRY Microsoft Query (filename extension). .qt QuickTime movie, binary file type (filename extension). . .QTM QuickTime Movie (filename extension). .R8L LaserJet landscape font .R8P LaserJet portrait font .RA RealAudio .RAM Real Audio .RAS Raster graphics - Sun .RAW Raw file format - bitmap (filename extension). .rc A filename extension found in many UNIX files (.newsrc, etc.) which means "run commands". .REC Windows Recorder macro file (filename extension). .REG Registration file (filename extension). .REP Report file (filename extension). .RFT RFT-DCA (filename extension). .RGB An SGI RGB image file .RIA Alpharel Group IV raster graphics .RIB Renderman graphics .RIC Roch FaxNet .RIF Fractal Painter bitmap (filename extension). .RIFF Resource Interchange File Format A multimedia file format; the Microsoft equivalent to Amiga IFF format. .RIX RIX virtual screen .RLA Wavefront raster image .RLC CAD Overlay ESP - Image Systems .RLE Run Length Encoded .RM Real Media. .RMI RIFF MIDI file .RND AutoShade format .RNL GTX Runlength raster graphics .RPT Report file (filename extension). .RTF Microsoft text and graphics .S Assembly language file - Unix .S3M MOD music file (filename extension). .SAM AmiPro .SAV Saved game (filename extension). .SBP IBM Storyboard graphics / Superbase text .SC Source Code - Paradox .SCM ScreenCam movie .SCP Dial-up networking script (filename extension). .SCR 1. Screensaver - Windows. 2. Screen Layout - dBASE. 3. Script for Apple's Disk Copy utility. .SCT Screen Capture Text - Lotus .SDL SmartDraw Library (filename extension). .SEA Self-Extracting Archive (Stuffit or Compact Pro) .SEG Segment (of a compressed file saved in segments with Stuffit or Compact Pro) .SEP TIFF bitmap (filename extension). .SET Setup parameters .SFL LaserJet landscape font .SFP LaserJet portrait font .SFS PCL 5 scalable font .shar UNIX shell archive (filename extension), which can be decoded by Unshar. .SHTML HTML file with embedded server-side includes (SSIs) (filename extension). .SI SoftImage image file .sig Signature A .sig file can be set up and automatically attached to outgoing email, newsgroup postings, etc. It includes the name and contact information of the sender, and may also have ASCII art, favorite quotes, etc. .SIT Stuffit compressed file .SLD AutoCAD slide .SLK Symbolic Link (SYLK) spreadsheet (filename extension). .SMI Self-Mounting Image. This file is a Macintosh Disk Image, similar to an .img file, but it does not require the use of Disk Copy. When the file is downloaded, a disk image appears on the desktop. The disk image will behave like a read-only disk. .SND Sound file .SNM Netscape mail (filename extension). .SPD Speedo scalable font .spx Screen Peace Extension .SQB SyQuest Backup (filename extension). .SRC A file used in the creation of .INI files for configuration settings (filename extension). .STY Style sheet - Ventura .SVX Amiga 8SVX sound (filename extension). .SWP Swap - temporary file (filename extension). .SYD Sysedit backup file (filename extension). .SYL SYLK spreadsheet format .SYNU SDSC Synu image .SYS System file .TAL Adobe Type Align .TAR Tar - Tape ARchive (filename extension). Tar is a UNIX method of archiving files, which can also be used by PCs. Tar archives files but does not compress them, so sometimes .tar files are compressed with other utilities, which produces extensions like .tar.gz, .tar.Z, and .tgz. Archive files with the .tar extension can be extracted in UNIX with tar or on a PC with WinZip or on the Mac with the program Tar. .tar.gz Combined filename extension for a file that has been archived using tar and then gzipped. .tar.z or .tar.Z Combined filename extension for a file that has been archived using tar and then zipped. .taz Another way of writing .tar.Z .TBK Asymetrix Toolbook (filename extension). .TDF Typeface definition - Speedo .TEX Tex or LaTex document .TFM Font metrics - Intellifont .TGA TARGA graphics .tgz Another name for .tar.z and .tar.gz .THEME Desktop theme - Windows 95 (filename extension). .THN Thumbnail (filename extension). .TIF TIFF graphics file .TIFF TIFF graphics file (filename extension). .TLB OLE Type Library (filename extension). .TMP Temporary file .TOC Table Of Contents (filename extension). .TRM Terminal settings - Windows (filename extension). .TTC TrueType compressed font .TTF TrueType font .TWF TabWorks File (file extension). .TX8 MS-DOS text (filename extension). .TXT ASCII text file .USL LaserJet landscape font .USP LaserJet portrait font .uu Uuencode compressed file .uue Uuencode file .VBP Visual Basic Project (filename extension). .VBX Visual Basic Extension .VDA Targa bitmap (filename extension). .VGR Ventura .VIFF Khoros Visualization image file .VLB Ventura Library (filename extension). .VOC Sound Blaster .VP Ventura Publisher (filename extension). .VST Targa bitmap (filename extension). .VUE Relational View - dBASE .VXD Virtual Device Driver (filename extension). .WAB Windows Address Book (filename extension). .WAV Sound file .WBK Microsoft Word Backup (filename extension). .WDB Microsoft Works Database (filename extension). .WID Ventura width table (filename extension). .WIN Windows backup file (filename extension). .WIZ Microsoft Word Wizard (filename extension). .WK1 Lotus 1-2-3, up to 2.01 .WK3 Lotus version 3 .WK4 Lotus version 4 .WKQ Quattro spreadsheet .WKS 1. Lotus Worksheet (filename extension). 2. Microsoft Works document (filename extension). .WLR VRML page .WMF Windows Metafile .WP WordPerfect .WPD 1. Windows Printer Description (filename extension). 2. WordPerfect Demo (filename extension). 3. WordPerfect Document (filename extension). .WPG WordPerfect Graphics .WPM WordPerfect macro .WPS Microsoft Works document .WPT WordPerfect Template (filename extension). .WRI Windows Write document .WRK Symphony spreadsheet .WS1 WordStar for Windows 1 document (filename extension). .WS2 WordStar for Windows 2 document (filename extension). .WS3 WordStar for Windows 3 document (filename extension). .WS4 WordStar for Windows 4 document (filename extension). .WS5 WordStar for Windows 5 document (filename extension). .WS6 WordStar for Windows 6 document (filename extension). .WS7 WordStar for Windows 7 document (filename extension). .WVL Wavelet compressed bitmap (filename extension). .X AVS X image file .XAR Corel Xara drawing (filename extension). .XBM X Bitmap .XFX JetFax .XIF Xerox Image Format (filename extension). .XLC Excel chart .XLK Microsoft Excel backup (filename extension). .XLM Microsoft Excel macro (filename extension). .XLS Excel worksheet .XLT Microsoft Excel template (filename extension). .XM MOD music format (filename extension). .XPM X Pixelmap .XWD X Window System window dump image .XXE Xxencoded file (filename extension). .YAL Arts & Letters click art (filename extension). .Z Unix compress file .ZIP File compressed using PKZIP .ZOO Zoo assistants A special kind of file used by Claris Works. Assistants guide the user through a task by asking a series of questions and then use the answers to perform a task. Assistants in Claris Works can be used to create such useful items as calendars, newsletters, stationery, labels, and address lists, to make footnotes within a file, to find documents, etc. bad fix A failed attempt to repair a computer bug; a fix that doesn't work or that introduces new and unexpected problems. The expression has cropped up a lot in relation to Y2K fixes. LHA A DOS compression program. Compressed files have the extension .lhz. MBX Message Base - Eudora (filename extension).