| Extension | Type | Characteristics |
|---|---|---|
| .aam | media file | MacroMedia Shockwave |
| .arc | archive file (obsolete) |
Open with PKZip or WinZip |
| .asp | web page | active server page – used to code Web pages that connect to databases |
| .au | audio | Sound file – open with player – used on older Web pages |
| .avi | video clip | Audio/Video Interleaved – movie clip – open with mplayer, IE, or Navigator with plugin |
| .bak | backup file | Used by many applications – often created automatically |
| .bat | application | DOS batch file – run by double-clicking in Win95 – edit with Notepad |
| .bmp | graphic file | Microsoft bitmap – open in MS Paint or graphics program |
| .cab | archive | Microsoft installation achive (cabinet file) – similar to .zip archive |
| .cfg | — | Configuration file |
| .cgi | — | Common Gateway Interface – used to exchange information with a server (often used with Perl) |
| .chk | — | Data recovered after running Checkdisk |
| .css | style sheet | plain text file containing web page style preferences |
| .csv | data | Comma Separated Value file – a way of presenting tabular data in a text file – usually viewed in MS Excel. |
| .dat | data file | Used by several applications. Not to be opened directly. |
| .dcr | media file | Macromedia Shockwave movie |
| .dir | media file | Macromedia Director file – provides animation and interactivity |
| .dll | dynamic link library | Software used by Windows to provide services to applications |
| .doc | document | Microsoft Word file |
| .dot | template | Microsoft Word template |
| .drv | device driver | Used to control hardware – (old) |
| .dtd | text | document type definition |
| .exe | application | self-extracting or executable file – run by double-clicking in Win95 |
| .faq | data file | Frequently Asked Questions – almost always a text file |
| .fla | media | Macromedia Flash animation file – requires Shockwave |
| .fnt | — | Font file |
| .gif | image | graphic in GIF format – open in web browser or graphics program |
| .gz | application | compressed archive file created by Gzip in the UNIX operating system |
| .hqx | archive | Compressed Macintosh file archive created by Binhex |
| .htm | text file | hypertext document [same as .html] – open in a web browser – edit in any word-processor or text editor |
 This dictionary explains the thousands of new terms which have come into use during the last few years. It includes the abbreviations of newsgroups, the language of e-commerce, and the scientific terms used to describe the structure of the Internet. It provides terms on the Web itself, software technology, security, and the arcane language of hackers. |
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| .ico | Windows icon | Open with an icon editor |
| .ini | — | Initialisation file |
| .jar | Java | Java compressed archive file |
| .jav | Java | cross platform programming language used to create complex interactive forms and special effects |
| .jpg | image | Graphic in JPEG format (Joint Photographic Experts Group) View with web browser or image editing program |
| .js | JavaScript | part of Web page used to create interactive effects such as mouse roll-overs and pop-up boxes |
| .jso | — | Java server page |
| .kbd | data file | Keyboard layout data |
| .log | data file | Created by many applications – usually a text file – edit in any text editor |
| .mdb | database | Database file created by Microsoft Access, a widely-used desktop relational database program; contains the database structure (tables and fields) and database entries (table rows) as well as data entry forms, queries, stored procedures, reports, and database security settings. |
| .mid | audio | audio file in MIDI format |
| .mov | video | QuickTime movie – view using IE or Netscape using plug-in |
| .mp3 | audio | Audio file in MP3 format – CD-quality sound, with 10x compression |
| .mpg | movie | Video movie in MPEG format (Motion Picture Experts Group) |
| .odf | data | OpenDocument Formula. Spreadsheet formula used by OpenOffice.org and StarOffice Calc; allows the results of calculations performed within the spreadsheet to be automatically entered into one or more cells; based on the OASIS OpenDocument standard and formatted in XML. |
| .old | — | Backup file (generic) |
| application | Portable Document Format – requires Adobe Acrobat reader | |
| .pl | application | Perl source file – text file, editable in any text editor |
| .png | image | graphic in Portable Network Graphics format – can work on all platforms |
| .ppt | application | Microsoft PowerPoint file – used for creating slides and overhead presentations |
| .pub | — | Microsoft Publisher page template file |
| .ram | audio | Real Audio file – open in browser with RealAudio plug-in |
| .rtf | application | Rich Text Format – word-processor file with formatting codes |
| .scr | screen saver | |
| .sea | application | Self-extracting archive – Apple-Mac – requires Stuffit |
| .sig | signature | Appended to outgoing email messages – editable in text editor |
| .swf | media | Macromedia Shockwave Flash animation movie |
| .sys | — | DOS system file – device driver or hardware configuration info |
| .tar | application | file archive created in the Unix operating system |
| .tar.gz | application | .tar archive compressed by Gzip |
| .tif | image | Tagged Image File format – graphic file – editable in graphics program |
| .tmp | — | temporary file – used by many programs |
| .ttf | — | True Type Font file – view with fontview |
| .txt | text | contains only ASCII code – also called ‘text file’ – editable in any text editor |
| .wav | audio | Sound file in Waveform format |
| .wsz | graphics | Winamp skin – visual interface for audio control board |
| .xls | application | Microsoft Excel worksheet file |
| .xml | Web page | extensible markup language – a plain text file for web pages |
| .zip | application | compressed file – open with WinZip or PKZip |
© Roy Johnson 2002