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Appendix. Common Filename Extensions

This appendix lists many of the most common filename extensions that you'll find on your system, that you might download, or that you have received over the Internet.

Extensions were universally used on DOS and Windows 3.1 files, but Microsoft has gone to some difficulty to hide them in Windows Vista. This is unfortunate, because they play a major role in the way Windows decides what application will be used to open a file, as well as which files will be visible when opening files in a given application. Although direct associations are made between some files without extensions and the applications needed to open them, in most cases the association is between an extension and a Registry setting that tells the system what application to use. To enable the display of filename extensions, open Windows Explorer, go to Control Panel [Appearance and Personalization] Folder Options View tab, and turn off the "Hide extensions for known file types" option.

If you double-click on an unknown file type, the Open With dialog box appears, allowing you to make a new association. To subsequently change an association once it has been made, right-click on the file and select Open With, or select Properties and then click Change.

Table D-1 list many system extensions, but third-party applications use literally thousands of file formats. And you might be thrown off by an improperly named file, or by an application using a standard filename extension for a nonstandard purpose. You can open many of these file types only if you have the appropriate application. If all else fails, you can open just about any file in Notepad; although nontext files will look mostly like gibberish, you may get clues in some of the excerpts of readable text you'll see.

If you still can't find a file's type from its extension, there are several more good sources:

  • Microsoft has put together a simple "extension finder" web site, intended for use with the "Use the Web service to find the correct program" feature that appears when you try to open a file with an extension that Windows doesn't recognize. The address for this site is:

    http://shell.windows.com/fileassoc/0409/xml/redir.asp?Ext={your extension}

    where {your extension} is the filename extension (without the dot) that you want to learn more about. For example, to find out about the .sit extension, you'd go to:

    http://shell.windows.com/fileassoc/0409/xml/redir.asp?Ext=sit

  • Use an ordinary search engine such as Google (http://www.google.com) to search for references to the filename extension. For example, to find out about the .hqx extension, try searching for "hqx file" (with the quotes).

Table D-1. Common filename extensions

Extension

Description

.$$$

Temporary file

.1st

ASCII text file (e.g., READ.1st)

.3ds

3D Studio file

.3gp, .3gpp

Video clip created on a cell phone or other mobile device

.3gr

Windows Video Grabber datafile

.8m

PageMaker Printer font with Math 8 extended character set

.8u

PageMaker Printer font with Roman 8 extended character set

.abf

Adobe Binary Font

.abm

Photo album

.abs

MPEG audio sound file

.aca

Microsoft Agent Character file

.ace

Ace Archiver compressed file

.acf

Microsoft Agent Character file

.ad

AfterDark screensaver

.adi

AutoCAD graphics

.adx

Archetype designer document

.afi

Truevision bitmap graphics

.afm

ATM Type 1 font metric ASCII data for font installer

.ai

Adobe Illustrator vector graphics

.ans

ANSI graphics; character animation

.aps

Microsoft Visual C++ file

.arc

Compressed file archive

.arf

Automatic Response File

.arj

Compressed file archive created by ARJ

.asc

ASCII text file

.ascx

Microsoft ASP.NET user control file

.asd

Word for Windows Autosave file

.asm

Assembly source code file

.asmx

Microsoft .NET Web Service file

.asp

Microsoft Active Server Page

.aspx

Microsoft ASP.NET file

.asx

Microsoft Windows Media Active Stream Redirector file

.asx

Windows Media Streaming video shortcut

.atm

Adobe Type Manager data/information

.au

Audio file used on older web pages

.avi

Video for Windows Audio Video Interleaved movie clip

.awm

Animation Works movie

.b3d

3D Builder file

.bak

Backup file (generic)

.bas

Basic source code file

.bat

DOS batch file

.bco

Bitstream Outline font description

.bdr

Microsoft Publisher Border

.bez

Bitstream Outline font description

.bga

Bitmap graphics

.bib

Bibliography (ASCII)

.bin

Binary file

.bit

Bitmap X11

.bkf

Microsoft backup file

.bkw

FontEdit mirror image of font set

.bm

Bitmap graphics

.bmf

Corel image file

.bmp

Windows bitmap

.bsc

Microsoft Fortran Pwbrmake object file

.bup

Backup file (generic)

.c

C source code file

.c++

C++ source code file

.cab

Microsoft installation archive Cabinet file

.cas

Comma-delimited ASCII file

.cc

C++ source code file

.ccb

Visual Basic animated button configuration

.cel

Autodesk AnimatorLumena Graphics

.cfg

Configuration file

.cgi

Common Gateway Interface script

.cgm

Computer Graphics Metafile vector graphics

.chd

FontChameleon Font descriptor

.chk

ChkDsk recovered data

.cif

Caltech Intermediate Format graphics

.cif

Easy CD Creator CD image file

.class

Compiled Java class file

.cls

C++ class definition file

.cmf

Creative Music File FM-music file

.cnt

Helpfile contents

.col

Microsoft Multiplan spreadsheet

.contact

Windows Contacts contact entry

.cpi

Colorlab Processed Image bitmap graphics

.cpi

DOS Code Page Information file

.cpp

C++ source code file

.cps

Colored PostScript files

.crf

Microsoft MASMZortech C++ cross-reference

.cs

C# source code file

.csv

Comma Separated Value text file format (ASCII)

.ctx

Microsoft online guides Course TeXt file

.ctx

Pretty Good Privacy RSA System cipher text file

.cvp

WinFax cover page

.cvs

Canvas graphics

.dat

Datafile (generic)

.dbg

Microsoft C/C++ symbolic debugging information

.dcr

Shockwave file

.dcs

CYMK format bitmap graphics

.ddb

Bitmap graphics

.dev

Device driver (old)

.dib

Device-Independent Bitmap bitmap graphics

.dic

Lotus Notes/Domino dictionary file

.dip

Graphics

.diz

Description In Zip description file

.dlg

Microsoft Windows SDK dialog resource script file

.doc

Microsoft Word document

.dot

Word for Windows template

.drv

Device driver (old)

.dvr-ms

Windows Media Center recorded video file

.dxf

AutoCAD Drawing Interchange File format vector graphics

.emf

Enhanced Metafile graphics

.eml

Microsoft Outlook Express electronic mail

.eps

Adobe Illustrator Encapsulated PostScript vector graphics

.evt

Event log

.exe

Executable program

.f77

Fortran 77 source code file

.faq

Frequently Asked Questions text file

.fax

Incoming fax

.fd

Microsoft Fortran Declaration file

.ff

Agfa Compugraphics Outline font description

.ffl

Microsoft Fast Find file

.ffo

Microsoft Fast Find file

.ffx

Microsoft Fast Find file

.fhx

Macromedia FreeHand version x vector graphics

.fh4

Macromedia FreeHand 4.x vector graphics

.fi

Microsoft Fortran Interface file

.fif

Fractal Image Format file

.flc

Autodesk Animator animation

.fli

Autodesk Animator animation

.fm

FrameMaker document

.fm1

Lotus 1-2-3 release 2.x spreadsheet

.fm3

Lotus 1-2-3 release 3.x spreadsheet

.fmb

WordPerfect for Windows File Manager button bar

.fnt

Font file

.fon

Windows 3.x font library font file

.fot

Windows Font Installer installed TrueType font

.frf

FontMonger Font

.frm

Visual Basic form

.fts

Windows Help full-text search index file

.fxs

WinFax fax transmit format graphics

.gadget

Windows Gadget

.gcd

Graphics

.gwi

Groupwise file

.gz

GNU ZIP compressed file archive created by GZIP

.h

Header file (used with .c source code)

.h++

C++ header file

.hdf

Help Development Kit help file

.hgl

HP Graphics Language graphics

.hh

C++ header file

.hlp

Help information

.hpf

PageMaker HP LaserJet fonts

.hpj

Microsoft Help Compiler help project

.hqx

Compressed Macintosh file archive created by Binhex

.htm

HyperText Markup Language document

.html

HyperText Markup Language document

.htt

HyperText template

.hxx

C++ header file

.ical

iCalendar file

.icb

Bitmap graphics

.icn

Icon source code file

.ilk

Microsoft ILink incremental linker outline of program's format

.imp

Lotus Improv spreadsheet

.imz

Compressed floppy image

.inc

Include file (programming)

.inf

Information text file

.inf

Install script/Driver information

.ini

Initialization file

.ion

File description (e.g., descript.ion)

.iso

CD or DVD image file

.isr

Microsoft Streets & Trips route file

.jar

Java archive file

.jas

Graphics

.java

Java source code file

.jff

JPEG File Interchange Format bitmap graphics

.jpg

JPEG image file

.jsp

Java Server Page

.jtf

JPEG Tagged Interchange Format bitmap graphics

.kar

MIDI file with karaoke word track

.key

Keyboard macros

.lbm

DeluxePaint bitmap graphics

.ldb

Microsoft Access data

.lex

Lexicon

.lha

Compressed file archive created by LHA/LHARC

.lib

Library file (programming)

.lif

Compressed file archive

.lnk

Windows shortcut

.log

Logfile (text)

.lrf

Microsoft C/C++ Linker response file

.lwz

Microsoft Linguistically Enhanced Sound file

.lzh

Compressed file archive created by LHA/LHARC

.lzs

Compressed file archive created by LARC

.lzx

Compressed file archive

.m3u

Media playlist

.mak

Makefile

.mak

Visual Basic project file

.man

Command manual

.map

Color palette

.map

Linker map file

.mat

Matlab datafile

.mbx

Eudora mailbox

.mda

Microsoft Access data

.mdb

Microsoft Access database

.mdl

3D Design Plus model

.mdt

Microsoft ILink incremental linker data table

.me

ASCII text file (e.g., READ.me)

.mht

Microsoft MHTML document

.mic

Microsoft Image Composer file

.mif

FrameMaker Maker Interchange Format

.mim

MIME file (used for email attachments)

.mk

Makefile

.mke

Microsoft Windows SDK makefile

.mmf

Microsoft Mail mail message file

.mny

Microsoft Money Account book

.mov

QuickTime movie

.mp2

MPEG audio or video file

.mp3

MPEG Layer 3 audio file

.mp4

MPEG-4 movie

.mpc

Microsoft Project Calendar file

.mpe

MPEG movie clip

.mpd

Microsoft Project database file

.mpg

MPEG movie

.mpp

Microsoft Project project file

.mpv

Microsoft Project view file

.mrb

Microsoft C/C++ Multiple Resolution Bitmap graphics

.msc

Microsoft C makefile

.msi

Windows Installer file

.mso

Microsoft FrontPage file

.msp

Microsoft Paint bitmap graphics

.mst

Microsoft Windows SDK setup script

.msw

Microsoft Word text file

.mswmm

Windows Movie Maker project

.mxt

Microsoft C data

.nfo

Info file (ASCII)

.nlm

Netware Loadable Module

.nsf

Lotus Notes/Domino database

.nt

Windows NT Startup files

.ntf

Lotus Notes/Domino template file

.nws

Info text file

.nxt

NeXT format sound

.ofm

Adobe font

.oft

Microsoft Outlook Item template

.ogg

Ogg Vorbis music file

.old

Backup file (generic)

.one

Microsoft Office OneNote file

.ost

Microsoft Outlook Offline file

.out

Output file (ASCII)

.p65

Adobe PageMaker v6.5

.pab

Microsoft Outlook personal address book

.pak

Compressed file archive created by PAK; also a Quake game file

.pal

Color palette

.pas

Pascal source code file

.pb

WinFax Pro phonebook

.pbi

Microsoft Source Profiler profiler binary input

.pbm

Portable Bit Map graphics

.pbo

Microsoft Source Profiler profiler binary output

.pbt

Microsoft Source Profiler profiler binary table

.pcc

PC Paintbrush Cutout picture vector graphics

.pcd

Kodak PhotoCD graphics

.pcf

Microsoft Source Profiler profiler command file

.pch

Microsoft C/C++ precompiled header

.pcl

HP Printer Control Language HP-PCL graphics data

.pcx

PC Paintbrush bitmap graphics

.pda

Bitmap graphics

.pdb

Palm database

.pdd

Adobe PhotoDeluxe image

.pdf

Adobe Portable Document Format

.pfb

Type 1 font file

.pfm

Type 1 font metric file

.pgm

Portable Grayscale bitmap graphics

.pgp

Pretty Good Privacy RSA System Support file

.ph

Microsoft C/C++ Phrase-table

.ph

Perl header file

.pic

PC Paint bitmap graphics

.pka

Compressed file archive created by PKARC

.pkg

NeXT/Mac OS X Installer archive

.pl

Perl source code file

.pl1

3D Home Architect room plan

.pm3

PageMaker 3 document

.pm4

PageMaker 4 document

.pm5

PageMaker 5 document

.png

Portable Network Graphics bitmap

.pnm

Graphics file (Portable aNy Map)

.pov

Persistence Of Vision raytraced graphics image

.ppd

Acrobat PostScript Printer Description

.ppm

Portable Pixel Map graphics

.ppt

PowerPoint presentation

.pr2

Adobe Persuasion 2.x presentation

.pr3

Adobe Persuasion 3.x presentation

.prc

Palm resource file

.prj

Project

.ps

PostScript file

.psd

Photoshop image

.pst

Microsoft Outlook personal folder

.pt3

PageMaker 3 template

.pt4

PageMaker 4 template

.pub

Microsoft Publisher Page template

.pub

Pretty Good Privacy RSA System Public key ring file

.pwl

Password List

.py

Python script file

.pyc

Compiled Python script file

.qbw

QuickBooks for Windows spreadsheet

.qdat

QuickTime Installer cache

.qdb

Quicken datafile

.qdf

Quicken for Windows datafile

.qdt

Quicken datafile

.qfl

Quicken Family Lawyer file

.qfx

QuickLink fax

.qic

Backup set for Microsoft Backup

.qif

Quicken Interchange Format

.qlb

Microsoft C/C++ Quick library

.qlp

QuickLink Printer driver

.qt

QuickTime movie

.qxd

QuarkXPress Document

.qxl

QuarkXPress Element library

.r00, .r01

Compressed file archive created by RAR (supplemental to .rar)

.ra

RealMedia file

.ram

RealMedia shortcut

.rar

Compressed file archive created by RAR

.ras

Sun Rasterfile graphics

.rc

Microsoft C/C++, Borland C++ Resource script

.rcg

Netscape newsgroup file

.rdp

Remote Desktop Connection Profile

.ref

Cross-reference

.res

Microsoft C/C++, Borland C++ Compiled resource

.rib

3DReality Graphics in Renderman format

.rif

Fractal Design Painter Riff bitmap graphics

.rl4

Bitmap graphics

.rl8

Bitmap graphics

.rlc

Graphics 1-bit/pixel scanner output

.rtf

Windows Word Rich Text Format text file (Word)

.rtf

Windows Help file script

.rvp

Microsoft Scan Configuration file

.sav

Configuration file

.sav

Backup file

.sbi

Creative Labs Sound Blaster Instrument file

.sco

High score

.sdf

System Data Format (ASCII)

.sea

Self-Extracting compressed Macintosh file Archive

.search-ms

Windows Vista saved search folder

.sec

Pretty Good Privacy RSA System Secret key ring file

.sfi

HP LaserJet landscape printer font

.sif

Windows NT Setup Setup Installation Files info

.sit

Compressed Macintosh archive created by STUFFIT

.sng

MIDI sound Song

.spc

Microsoft Multiplan Program

.srp

QuickLink Script

.ssm

RealPlayer Standard Streaming Metafile

.sts

Microsoft C/C++ Project status info

.swf

ShockWave Flash object

.sys

Windows or DOS System filedevice driver or hardware configuration info

.tar

Compressed file archive created by TAR

.taz

Compressed file archive created by TAR and COMPRESS (equiv. to .tar.Z)

.tga

Truevision Targa bitmap graphics

.tgz

Compressed file archive created by TAR and GNUzip (equiv. to .tar.gz)

.thm

Microsoft Clipart Gallery database

.tif

Tagged Image File Format bitmap graphics

.tis

MahJongg 3.0 Tile set

.tlb

Visual C++ Type library

.tmp

Temporary file

.toc

Eudora Table Of Contents

.torrent

BitTorrent

.tpz

Compressed file archive created by TAR and GNUzip (equiv. to .tar.gz)

.ttf

TrueType Font file

.txt

Text file

.tym

PageMaker Time Stamp

.tz

Compressed file archive created by TAR and COMPRESS (equiv. to .tar.Z)

.uhs

Universal Hint System

.uu

Compressed ASCII file archive created by UUEncode/UUDecode

.uue

Compressed ASCII file archive created by UUEncode/UUDecode

.vbs

Visual Basic Script file

.vbx

Visual Basic Visual Basic eXtension (custom control)

.vcf

VCard file

.vcw

Microsoft Visual C++ Visual workbench information

.vda

Bitmap graphics

.vmc

Acrobat reader Virtual Memory Configuration

.vnc

VNC connection profile

.vob

DVD video movie file

.voc

Creative Voice file Digitized samples

.vds

Visio drawing file

.vue

3D Studio animation

.vxd

Virtual device driver

.wab

Outlook (Windows Address Book) file

.wad

Doom game file

.wav

Waveform audio file

.wb1

Quattro Pro Notebook

.wb2

Quattro Pro Spreadsheet

.wba

Winace ZIP file

.wba

WindowBlinds Compressed Skin for Windows XP

.wbk

WordPerfect for Windows document/workbook

.wcm

Microsoft Works Data transmission file

.wdb

Microsoft Works Database

.wdl

Windows XP Watchdog Log file

.wfx

WinFax datafile

.wiz

Microsoft Publisher Page wizard

.wk1

Lotus 1-2-3 version 2.xSymphony 1.1+ spreadsheet

.wk3

Lotus 1-2-3 version 3.x spreadsheet

.wk4

Lotus 1-2-3 version 3.4 spreadsheet

.wkb

WordPerfect for Windows document

.wkq

Quattro spreadsheet

.wks

Lotus 1-2-3 version 1ASymphony 1.0Microsoft Works spreadsheet

.wma

Microsoft Windows Media Active Streaming file

.wmf

Windows MetaFile vector graphics

.wmv

Microsoft Active Streaming file

.wn

NeXT WriteNow Text

.wp

WordPerfect 4.2 text file

.wp5

WordPerfect 5.x document

.wpm

WordPerfect macros

.wps

Microsoft Works text document

.wq1

Quattro Pro spreadsheet

.wri

Windows Write text file

.wrl

VRML file

.wrml

VRML file

.wsz

WinAmp Skin ZIP file

.xla

Microsoft Excel Add-in macro sheet

.xlb

Microsoft Excel data

.xlc

Microsoft Excel Chart document

.xll

Microsoft Excel Excel Dynamic Link Library

.xlm

MS Excel Macro sheet

.xlr

Microsoft Works file

.xls

Microsoft Excel worksheet

.xlt

Microsoft Excel template

.xlw

Microsoft Excel workbook

.xmi

Compressed extended MIDI music

.xml

XML document

.xnk

Microsoft Exchange Shortcut

.xps

XPS Document (Paper Specification)

.xsl

XSL stylesheet

.xwk

Crosstalk keyboard mapping

.xwp

Crosstalk session

.z

Compressed file archive created by COMPRESS

.z3

Infocom game module

.z5

Inform game module

.zip

Compressed ZIP file archive

.zoo

Compressed file archive created by ZOO



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