Engineer must know these extension..!

Text Files

.doc    Microsoft Word Document
.docx    Microsoft Word Open XML Document
.log    Log File
.msg    Outlook Mail Message
.pages    Pages Document
.rtf    Rich Text Format File
.txt    Plain Text File
.wpd    WordPerfect Document
.wps    Microsoft Works Word Processor Document

Data Files

.accdb    Access 2007 Database File
.blg    Windows Binary Performance Log File
.csv    Comma Separated Values File
.dat    Data File
.db    Database File
.efx    eFax Document
.mdb    Microsoft Access Database
.pdb    Program Database
.pps    PowerPoint Slide Show
.ppt    PowerPoint Presentation
.pptx    Microsoft PowerPoint Open XML Document
.sdb    OpenOffice.org Base Database File
.sdf    Standard Data File
.sql    Structured Query Language Data
.uccapilog    Microsoft UCC API Log File
.vcf    vCard File
.wks    Microsoft Works Spreadsheet
.xls    Microsoft Excel Spreadsheet
.xlsx    Microsoft Excel Open XML Document
.xml    XML File

Image Files

Raster Image Files

.bmp    Bitmap Image File
.gif    Graphical Interchange Format File
.jpg    JPEG Image File
.png    Portable Network Graphic
.psd    Photoshop Document
.psp    Paint Shop Pro Image File
.thm    Thumbnail Image File
.tif    Tagged Image File

Vector Image Files

.ai    Adobe Illustrator File
.drw    Drawing File
.eps    Encapsulated PostScript File
.ps    PostScript File
.svg    Scalable Vector Graphics File

3D Image Files

.3dm    Rhino 3D Model
.dwg    AutoCAD Drawing Database File
.dxf    Drawing Exchange Format File
.pln    ArchiCAD Project File

Page Layout Files

.indd    Adobe InDesign File
.pct    Picture File
.pdf    Portable Document Format File
.qxd    QuarkXPress Document
.qxp    QuarkXPress Project File
.rels    Open Office XML Relationships File

Audio Files

.aac    Advanced Audio Coding File
.aif    Audio Interchange File Format
.iff    Interchange File Format
.m3u    Media Playlist File
.mid    MIDI File
.mp3    MP3 Audio File
.mpa    MPEG-2 Audio File
.ra    Real Audio File
.wav    WAVE Audio File
.wma    Windows Media Audio File

Video Files

.3g2    3GPP2 Multimedia File
.3gp    3GPP Multimedia File
.asf    Advanced Systems Format File
.asx    Microsoft ASF Redirector File
.avi    Audio Video Interleave File
.flv    Flash Video File
.mov    Apple QuickTime Movie
.mp4    MPEG-4 Video File
.mpg    MPEG Video File
.rm    Real Media File
.swf    Flash Movie
.vob    DVD Video Object File
.wmv    Windows Media Video File

Web Files

.asp    Active Server Page
.cer    Internet Security Certificate
.csr    Certificate Signing Request File
.css    Cascading Style Sheet
.htm    Hypertext Markup Language File
.html    Hypertext Markup Language File
.js    JavaScript File
.jsp    Java Server Page
.php    Hypertext Preprocessor File
.rss    Rich Site Summary
.tvpi    TitanTV Television Listing File
.tvvi    TitanTV Television Listing File
.xhtml    Extensible Hypertext Markup Language File

Font Files

.fnt    Windows Font File
.fon    Generic Font File
.otf    OpenType Font
.ttf    TrueType Font

Plugin Files

.8bi    Photoshop Plug-in
.plugin    Mac OS X Plug-in
.xll    Excel Add-In File

System Files
.cab    Windows Cabinet File
.cpl    Windows Control Panel
.cur    Windows Cursor
.dll    Dynamic Link Library
.dmp    Windows Memory Dump
.drv    Device Driver
.key    Security Key
.lnk    File Shortcut
.sys    Windows System File

Settings Files

.cfg    Configuration File
.ini    Windows Initialization File
.keychain    Mac OS X Keychain File
.prf    Outlook Profile File

Executable Files

.app    Mac OS X Application
.bat    DOS Batch File
.cgi    Common Gateway Interface Script
.com    DOS Command File
.exe    Windows Executable File
.pif    Program Information File
.vb    VBScript File
.ws    Windows Script

Compressed Files

.7z    7-Zip Compressed File
.deb    Debian Software Package
.gz    Gnu Zipped Archive
.pkg    Mac OS X Installer Package
.rar    WinRAR Compressed Archive
.sit    Stuffit Archive
.sitx    Stuffit X Archive
.tar.gz    Tarball File
.zip    Zipped File
.zipx    Extended Zip File

Encoded Files

.bin    Macbinary Encoded File
.hqx    BinHex 4.0 Encoded File
.mim    Multi-Purpose Internet Mail Message File
.uue    Uuencoded File

Developer Files

.c    C/C++ Source Code File
.cpp    C++ Source Code File
.java    Java Source Code File
.pl    Perl Script

Backup Files

.bak    Backup File
.bup    Backup File
.gho    Norton Ghost Backup File
.ori    Original File
.tmp    Temporary File

Disk Files

.dmg    Mac OS X Disk Image
.iso    Disc Image File
.toast    Toast Disc Image
.vcd    Virtual CD

Game Files

.gam    Saved Game File
.nes    Nintendo (NES) ROM File
.rom    N64 Game ROM File
.sav    Saved Game

Misc Files


.dbx    Outlook Express E-mail Folder
.msi    Windows Installer Package
.part    Partially Downloaded File
.torrent    BitTorrent File
.yps    Yahoo! Messenger Data File