Apple Macintosh Server and Webhosting: After Hours Consulting
Macintosh Advocate

What do those file names mean?

At some time in your computing experience, you'll come across an unknown file -- sent to you by a friend or colleague.  If it is a Mac file, you can normally open it with a double-click of the mouse.  But what if it isn't a Mac file -- or it's a Mac file which has been compressed or encoded to travel the Internet?  The file name can give you important clues as to what kind of file you've been sent, and what software you may need to use to open the file.

Here are some email etiquette suggestions for folks who receive files on floppies or over the Internet to make your life easier:

Step 1: Always ask your sender to ask you BEFORE they send a file whether they may do so, and how large the file is -- and return the favor to your recipients.

Step 2: Always ask the sender to tell you what the file is and the software they used to create it, including version number.

Step 3: Always scan a file with the latest update of your virus software BEFORE opening a file (Microsoft products in particular are prone to virus problems such as Macro viruses).

DOS-based operating systems (such as those PCs using Windows) normally place a three-character extension on the end of a file name to indicate the type of application or program which generated the file.  Other computer systems or applications may use a single, two or 4-character extension.  The table below indicates common file types and what you can do to open them without ending up with a screen full of garbled characters. 

So, you've received your mystery file.  What to do now?  Here, we use the generic "document" as the file's name, and include the extension ".xxx".

Step 4: Always make a duplicate copy of the file before attempting to open it, so in case your operations corrupt the original, you have a spare.

The "solution" listed below is a suggestion that you use the listed kind of application to open the file. Resist the urge to simply double-click on a file, unless you know exactly what that file is and that you have a version of software which can handle it. Often you will have better success opening the mystery file from within the application.

Step 5: Find a match for your file extension from the table below to determine what kind of software package may be able to open the mystery file.

Step 6: Launch the application first, then select "Open" (from your File menu), and select the mystery file from within the dialog box).

Most of the time, you'll be able to open the file.  But sometimes, even if you do everything right, a file may not open properly -- there are simply too many formats and versions of applications available for any cross-reference table to cover all of the possibilities.  We know of over 2300 file types with filename extensions -- with only the most popular and common listed below.  If you have a file you absolutely need to access, contact us about our conversion pricing.

We do not endorse any particular software package.  Software suggestions listed within the table or in the suggestion section below the table are simply some of the proven solutions available. Also, it is not uncommon to have a file formatted several ways if it has traveled on the Internet, possibly compressed or converted during its travels.  To translate a file successfully, work from right-to-left:  A file named "document.txt.sit.hqx" would need to be decoded from HQX first (the .hqx tells you this), then decompressed from Stuffit (the .sit tells you this), then treated like a text file (the .txt tells you this), so pay careful attention to the name.  Please let us know if we should add a filetype not listed below.

After Hours File Identifier Table

 File Name

What It May Mean

A Possible Solution


 a 669 MOD sound file

  open (and listen) with a sound or QuickTime app


 an Amiga 8MED sound file

  open (and listen) with a sound or QuickTime app


 an Amiga sound file (8 bit)

 open (and listen) with Apple's movieplayer or QuickTime app


 an AIFF sound file

 open (and listen) with Apple's movieplayer or QuickTime app


 an AIFF sound file

 open (and listen) with Apple's movieplayer or QuickTime app


 a compressed AIFF sound file

 open (and listen) with Apple's movieplayer or QuickTime app

 an ALAW sound file

 open (and listen) with Apple's movieplayer or QuickTime app


 an animated NeoChrome graphic file

 open with a graphic app or utility


an Arc[hive] (Windows) file

decompress with commercial Stuffit or Stuffit Expander/DropStuff


an Arj Archive file

decompress with DeArj or similar utility like Stuffit Expander


 an Amber graphic file

 open with a graphic app or utility


an ASCII document from a PC

open with a word processor


an ASCII document from a PC

open with a word processor


a Windows Media document

open with Windows Media Player


 an avi movie file

 open (and view) with Apple's movieplayer or QuickTime app


a Macbinary file, probably from the net

decode with HQXer or similar utility like Stuffit Expander


 a C++ program file

 open with CodeWarrior or other C++ programming package


 a computer graphics meta file

 open with a graphic app or utility


 a C++ program file

 open with CodeWarrior or other C++ programming package


a Compact Pro file

decompress with Compact Pro, commercial Stuffit or Stuffit Expander/DropStuff


 a DR Halo image file

 open with a graphic app or utility


 a Canvas file

 open with Canvas


 a dBase data file

 open with a database


 a text document from a PC

open with a word processor


a database query (Excel)

open with Excel or convert


 a dv video movie file

 open (and view) with Apple's movieplayer or QuickTime app


 an Encapsulated PostScript file

 open with a graphic app or utility


 an Envoy file

 open with Envoy


an application (executable program) from DOS or Windows

run this program in an emulator (Virtual PC, SoftWindows, etc.) or on a compatibility card for the old CISC (386-486-Pentium) technology


a GIF graphic file

open with a graphic app or utility


a GZip (Windows) compressed file

decompress with Stuffit Expander


 a HP-GL/2 (plot) graphic file

 open with a graphic app or utility


a bin-hex'ed file, probably from the Internet

decode with HQXer or similar utility like Stuffit Expander

 a TRS-80 (Tandy) file

 geez, good luck. Try a word editor first, then maybe a graphic app


a html (www) file

open with a web browser


a html (www) file

open with a web browser

 document.ic1 document.ic2

 an Atair Degas graphic file

 open with a graphic app or utility


 an Amiga IFF graphic file

 open with a graphic app or utility


 an Amiga ILBM graphic file

 open with a graphic app or utility

document.ima   (or .image)

a Disk Copy file (Apple)

open file with Disk Copy (a virtual disk should mount on the desktop)


a Web query (Excel)

open with Excel or convert


a JPEG graphic file

open with a graphic app or utility


 an Amiga IFF graphic file

 open with a graphic app or utility


a LHa file

decompress with commercial Stuffit or Stuffit Expander/DropStuff


a Paperport file or
a MAX sourcecode file

open with the original app or a text edting / word processor

 an Amiga MED sound file

  open (and listen) with a sound or QuickTime app


a MIME Unix base64 file

decode with MPack or a similar MIME conversion utility


 a NeoChrome graphic file

 open with a graphic app or utility


 a PageMaker 6.5 windows file

 open with PageMaker or convert with QuarkExpress or InDesign


 an Atari STAG image   graphic file

 open with a graphic app or utility

 document.pc1 document.pc2 document.pc3

 an Atair Degas graphic file

 open with a graphic app or utility


 an animated PICTs graphic file

 open with a graphic app or utility


 a PaintBrush graphic file

 open with a graphic app or utility


an Acrobat file (Adobe)

open with Acrobat reader

a private file

decompress with Stuffit Expander

 document.pi1 document.pi2 document.pi3

 an Atair Degas graphic file

 open with a graphic app or utility


 a PICT graphic file

 open with a graphic app or utility


an AppleLink file

decompress with commercial Stuffit or Stuffit Expander/DropStuff

 a bitmap xv graphic file

 open with a graphic app or utility


 a Quark Xpress file

 open with Quark Xpress or convert with InDesign


 a text document from a PC (Rich Text Format)

 open with a word processor

document.scg document.sci document.scp document.scr document.scu

 a ColoRix or screen capture graphic file

 open with a graphic app or utility


a self-extracting compressed file

file should decompress when DC'd or with Stuffit Expander


a Stuffit compressed file

decompress with Stuffit Expander


a Self-Mounting file (Apple)

file should mount a virtual disk on the desktop when DC'd


an Atari Spectrum 512   graphic file

 open with a graphic app or utility


 an Amiga IFF sound file

  open (and listen) with Apple's movieplayer or QuickTime app


a TAR file

decompress with commercial Stuffit or Stuffit Expander/DropStuff


an ASCII document from a PC

open with a word processor


a GZip (Windows) file

decompress with Stuffit Expander


a TIFF graphic file

open with a graphic app or utility


 an Atari Tiny bitmap     graphic file

 open with a graphic app or utility


a UU file

decompress with Stuffit Expander


a UU file

decompress with Stuffit Expander


 a DESR VFF graphic image

 open with a graphic app or utility


 a dvd video movie file

 open (and view) with Apple's DVD player or QuickTime app


 a Wave sound file

open (and listen) with a sound or QuickTime app


a chart (Excel)

open with Excel or convert


a macro (Excel)

open with Excel


a spreadsheet (Excel)

open with a spreadsheet


a template (Excel)

open with a spreadsheet


a workspace (Excel)

open with Excel or convert


 a FastTrack MOD sound file

 open with a database

a Zip (Windows) file

decompress with Stuffit Expander

Here's a more complete list

select a letter:

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z - numbers/symbols


ABK Corel Draw AutoBackup
ACL Corel Draw 6 keyboard accelerator
ACM Used by Windows in the system directory
ACP Microsoft Office Assistant Preview file
ACT Microsoft Office Assistant Actor file
ACV OS/2 drivers that compress and decompress audio data
AD After Dark screensaver
ADB Appointment database used by HP 100LX organizer
ADD OS/2 adapter drivers used in the boot process
ADM After Dark MultiModule screensaver
ADP Used by FaxWorks to do setup for fax modem interaction
ADR After Dark Randomizer screensaver
AFM Adobe font metrics
AF2 ABC Flowchart file
AF3 ABC Flowchart file
AI Adobe Illustrator drawing
AIF Apple Mac AIFF sound
AIFC Similar to AIF
AIFF Similar to AIF
AIS ACDSee Image Sequence file
ALB JASC Image Commander album
ALL Arts & Letters Library
AMS Velvert Studio music module (MOD) file
ANC Canon Computer Pattern Maker file that is a selectable list of pattern colors
ANI Animated Cursor
API Application Program Interface file; used by Adobe Acrobat
APR Lotus Approach 97 file
APS Microsoft Visual C++ file
ARC LH ARC (old version) compressed archive
ARI Aristotle audio file
ARJ Robert Jung ARJ compressed archive
ART Xara Studio drawing
ART Canon Crayola art file
ASA Microsoft Visual InterDev file
ASD WinWord AutoSave
ASF Microsoft Advanced Streaming Format file
ASM Assembler language source file
ASP Active Server Page (an HTML file containing a Microsoft server-processed script)
ASP Procomm Plus setup and connection script
AST Claris Works "assistant" file
ASX Cheyenne Backup script
ASX Microsoft Advanced Streaming Redirector file
ATT AT&T Group 4 bitmap
AU UNIX sound file
AVI Microsoft Video for Windows movie
AWD FaxView document


BAK Backup file
BAT Batch file
BFC Windows 95 Briefcase document
BG Backgammon for Windows game
BI Binary file
BIF GroupWise initialization file
BIN Binary file
BK and BK$ Sometimes used to denote backup versions
BKS An IBM BookManager Read bookshelf
BMK An A bookmark file
BMP Windows or OS/2 bitmap
BM1 Apogee BioMenace data file
BRX A file for browsing an index of multimedia options
BSP Quake map
BS1 Apogee Blake Stone data file
BS_ Microsoft Bookshelf Find Menu shell extension
BTM Batch file used by Norton Utilities
BUN CakeWalk Audio Bundle file (a MIDI program)
B4 Helix Nuts and Bolts file


C C code
CAB Microsoft cabinet file (program files compressed for software distribution)
CAL CALS Compressed Bitmap
CAL Calendar schedule data
CAS Comma-delimited ASCII file
CAT IntelliCharge categorization file used by Quicken
CB Microsoft clean boot file
CCB Visual Basic Animated Button configuration
CCF Multimedia Viewer configuration file used in OS/2
CCH Corel Chart
CCM Lotus CC:Mail "box" (for example, INBOX.CCM)
CCO CyberChat data file
CCT Macromedia Director Shockwave cast
CDA CD Audio Track
CDF Microsoft Channel Definition Format file
CDI Phillips Compact Disk Interactive format
CDR Core Draw drawing
CDT Corel Draw template
CDX Corel Draw compressed drawing
CEL CIMFast Event Language file
CER Certificate file (MIME x-x509-ca-cert)
CFB Comptons Multimedia file
CFG Configuration file
CGI Common Gateway Interface script file
CGM Computer Graphics Metafile
CH OS/2 configuration file
CHK File fragments saved by Windows Disk Defragmenter or ScanDisk
CHM Compiled HTML file
CHP Ventura Publisher chapter
CHT ChartViewer file
CHT Harvard Graphics vector file
CIL Clip Gallery download package
CIM Sim City 200 file
CIN OS/2 change control file that tracks changes to an INI file
CK1 iD/Apogee Commander Keen 1 data file
CK2 iD/Apogee Commander Keen 2 data file
CK3 iD/Apogee Commander Keen 3 data file
CK4 iD/Apogee Commander Keen 4 data file
CK5 iD/Apogee Commander Keen 5 data file
CK6 iD/Apogee Commander Keen 6 data file
CLASS Java class
CLP Windows Clipboard file
CLS Visual Basic Class Module
CMD Command file for Windows NT (similar to a DOS .BAT file)
CMD DOS CP/M command file
CMD dBase-II program file
CMF Corel Metafile
CMP Address document
CMV Corel Move animation
CMX Corel Presentation Exchange image
CNF Configuration file used by Telnet, Windows, and other applications with varying internal formats
CNM Windows application menu options and setup file
CNQ Compuworks Design Shop file
CNT Windows (or other) system content files for the help index and other purposes
COB trueSpace2 object
COD Microsoft C compiler output as displayable machine language/assembler with original C as comments
COM Command file (program)
CPD Fax Cover document
CPE Fax Cover document
CPI Microsoft MS-DOS code page information file
CPL Control Panel extension
CPL Corel colour palette
CPP C++ code
CPR Corel Presents Presentation
CPT Corel Photo-Paint image
CPX Corel Presentation Exchange Compressed drawing
CRD Cardfile file
CRP Corel Presents Run-Time Presentation
CRT Certificate file
CSC Corel Script
CSP PC Emcee On-Screen image
CSS Cascading Style Sheet file (MIME)
CST Macromedia Director "Cast" (resource) file
CSV Comma-separated values file
CT Scitex CT Bitmap
CT A graphic file associated with the Paint Shop Pro Graphic Editor
CTL Used in general to mean a file containing control information. FAXWorks uses it to keep information about each fax sent and received.
CUE Microsoft Cue Cards data
CUR Windows Cursor
CUT Dr Halo bitmap
CV Corel Versions archive
CV Microsoft CodeView information screen
CWK Claris Works data file
CWS Claris Works template
CXT Macromedia Director protected (not editable) "Cast" (resource) file
CXX C++ source code file


DAT Data file
DAT WordPerfect Merge Data
DBF Aston-Tate dBASE database
DBX DataBeam image
DCR Shockwave file
DCS Desktop Color Separation file
DCX Fax image (based on PCX)
DDF BTRIEVE database
DEF SmartWare II data file
DEF C++ Definition
DER Certificate file
DIB Device-Independent Bitmap
DIC Dictionary
DIF Data Interchange Format spreadsheet
DIR Macromedia Director file
DIZ Description file
DLG C++ Dialogue Script
DLL Dynamic-Link Library
DMF X-Trakker music module (MOD) file
DOC FrameMaker or FrameBuilder document
DOC WordStar document
DOC WordPerfect document
DOC Microsoft Word document
DOT Microsoft Word document Template
DPR Borland Delphi project header file
DRV Driver
DRW Micrografx Designer/Draw
DSG DooM saved game
DSM Dynamic Studio music module (MOD) file
DSP Microsoft Developer Studio project
DSQ Corel QUERY file
DSW Microsoft Developer Studio workspace
DTF Symantec Q&A relational database data file
DUN Microsoft Dial-up Networking Export file
DV Digital video file (MIME)
DWD DiamondWare digitized file
DWG AutoCAD drawing, or older Generic CADD drawing format
DXF Drawing Interchange (eXchange) format,a text representation of the binary DWG format
DXR Macromedia Director protected (not editable) movie file


EMF Enhanced Windows Metafile
EML Microsoft Outlook Express mail message (MIME RFC 822)
ENC Encore file
EPS Encapsulated PostScript image
ER1 ERWin file
ERX ERWin file
EVY Envoy document
EWL Microsoft Encarta document
EXC Microsoft Word Exclusion Dictionary
EXE Executable file (program)


F77 FORTRAN file
F90 FORTRAN file
FAR Farandole Composer music module (MOD) file
FAV Microsoft Outlook navigation bar
FAX FAX Type image
FCL Cyber Audio Library link file
FDF Adobe Acrobat Forms Document file
FH3 Aldus Freehand 3 drawing
FIF Fractal image file
FITS CCD camera image
FLC AutoDesk FLIC animation
FLI AutoDesk FLIC animation
FLT Corel filter
FLT StarTrekker music module (MOD) file
FMB Oracle binary source code for form, version 4.0 and later
FML File Mirror List (GetRight)
FMT Oracle text format of form, version 4.0 and later
FMT Microsoft Schedule+ print file
FMX Oracle executable form, version 4.0 and later
FND Microsoft Explorer Saved Search file (Find applet)
FNG Font group file (Font Navigator)
FOG Fontographer font
FON System font
FOT Font-related file
FP FileMaker Pro file
FP1 Flying Pigs for Windows data file
FP3 FileMaker Pro file
FPX FlashPix bitmap
FRM Form
FRM FrameMaker or FrameBuilder document
FRM Oracle executable form version 3.0 and earlier
FRM Visual Basic form
FRM WordPerfect Merge form
FRX Visual Basic form stash file
FTS Full-Text Search index file resulting from using Find in the Windows help system Can be erased; will be rebuilt when needed
FW3 Framework III file
FW4 Framework IV file


GAL Corel Multimedia Manager album
GCD Generic (TM) CADD drawing (later versions)
GCP Ground Control Point file used in image processing of remote sensing data often to form map projections. CHIPS (CopenHagen Image Processing System) uses these files.
GED Graphic Environment Document (drawing)
GEM GEM metafile
GEN Ventura-Generated text file
GetRight GetRight Unfinished-Download file
GFC Patton&Patton Flowcharting 4 flowchart file
GFI Genigraphics Graphics Link presentation
GFX Genigraphics Graphics Link presentation
GID Windows 95 global index file (containing help status)
GIF CompuServe bitmap
GIM Genigraphics Graphics Link presentation
GIX Genigraphics Graphics Link presentation
GKS Gravis GripKey document
GNA Genigraphics Graphics Link presentation
GNX Genigraphics Graphics Link presentation
GRA Microsoft Graph
GRD Grid file, used in image processing of remote sensing data often to form map projections. CHIPS (CopenHagen Image Processing System) uses these files
GRP Program Manager Group
GTK Graoumftracker (old) music module (MOD) file
GT2 Graoumftracker (new) music module (MOD) file
GWX Genigraphics Graphics Link presentation
GWZ Genigraphics Graphics Link presentation
GZ Unix Gzip compressed file


H C program header
HED HighEdit document
HEL Microsoft Hellbender saved game
HEX Macintosh BinHex 2.0 file
HGL HP Graphics Language drawing
HLP Help file
HOG Lucas Arts Dark Forces WAD file
HPJ Visual Basic Help Project
HPP C++ program header
HQX Macintosh BinHex 4.0 file
HST History file
HT HyperTerminal
HTM Hypertext document
HTML Hypertext document
HTT Microsoft Hypertext Template
HTX Extended HTML template


ICA Citrix file
ICB Targa bitmap
ICL Icon Library file (an industry standard)
ICM Image Color Matching profile file
ICO Windows Icon
IDD MIDI Instrument Definition
IDF MIDI Instrument Definition (Windows 95 required file)
IDQ Internet Data Query file
IDX Symantec Q&A relational database index file
IGF Inset Systems metafile
IIF QuickBooks for Windows interchange file
ILBM A bitmap (graphic image) file
IMA WinImage file
IMG GEM image
INC Assembler language or Active Server include file
INF Information file
INI Initialization file
INP Oracle source code for form, version 3.0 and earlier
INS InstallShield install script
INS X-Internet sign-up file
IOF Findit document
IQY Microsoft Internet Inquiry file
ISO Lists the files on a CD-ROM; based on the ISO 9660 CD-ROM file system standard
ISP X-Internet sign-up file
ISU InstallShield uninstall script
IT Impulse Tracker music module (MOD) file
ITS Internet document set (possibly a Microsoft file)
IW Idlewild screensaver


JAR Java ARchive file (a compressed file for applets and related files)
JAVA Java source code
JBF Paint Shop Pro image browser file
JMP SAS JMPDiscovery chart-to-statistics file
JN1 Epic MegaGames Jill of the Jungle data file
JPEG JPEG compressed bitmap
JPG JPEG bitmap
JS JavaScript source code
JTF JPEG bitmap


KDC Kodak Photo-Enhancer
KFX KoFax Group 4 image
KYE Kye game data


LBM Deluxe Paint bitmap
LDB Microsoft Access lock file
LEG Legacy document
LES Logitech Entertainment system game profiles (same as REG file)
LHA Alternate file suffix for LZH
LIB Library
LIS Output file produced by a Structured Query Reporting (SQR) program
LNK Windows shortcut file
LOG Log file
LPD Helix Nuts and Bolts file
LRC Intel Video Phone file
LST List file
LWO Lightwave Object file
LWP Lotus Wordpro 96/97 file
LZH LH ARC compressed archive
LZS Skyroads data file


M1V MPEG-related file (MIME type 'mpeg')
M3D Corel Motion 3D animation
M3U MPEG URL (MIME audio file)
MAC MacPaint image
MAD Microsoft Access module
MAF Microsoft Access Form
MAK Visual Basic or MS Visual C++ Project
MAM Microsoft Access Macro
MAP Map file
MAP Duke Nukem 3D WAD game file
MAQ Microsoft Access Query
MAR Microsoft Access Report
MAS Lotus Freelance Graphics Smartmaster file
MAT Microsoft Access Table
MAX Paperport file
MAZ Hover maze data
MB1 Apogee Monster Bash data file
MCC Dialer10 calling card
MCS MathCAD image
MCW Microsoft Word for Macintosh document
MDA Microsoft Access add-in
MDB Microsoft Access database
MDE Microsoft Access MDE file
MDL Digital Tracker music module (MOD) file
MDL Quake model file
MDN Microsoft Access blank database template
MDW Microsoft Access Workgroup
MDZ Microsoft Access wizard template
MED Music Editor, OctaMED music module (MOD) file
MER Format for interchanging spreadsheet/database data; recognized by Filemaker, Excel, and others
MET Presentation Manager metafile
MHTM MHTML document (MIME)
MI Miscellaneous
MIC Microsoft Image Composer file
MID MIDI music
MMF Microsoft Mail File
MMM Microsoft Multimedia Movie
MOD FastTracker, StarTrekker, Noise Tracker (etc.) music module file
MOD Microsoft Multiplan spreadsheet
MOV QuickTime for Windows movie
MPA MPEG-related file (MIME type 'mpeg')
MPE MPEG animation
MPEG MPEG animation
MPG MPEG animation
MPP Microsoft Project file
MPP CAD drawing file format
MP2 MPEG Audio Layer 2 file (MIME video file)
MP3 MPEG Audio Layer 3 (AC3) file
MSG Microsoft Mail message
MSN Microsoft Network document
MSP Microsoft Paint bitmap
MTM MultiTracker music module (MOD) file
MUS Music
MVB Microsoft Multimedia Viewer file
MWP Lotus Wordpro 97 Smartmaster file


NAP NAP Metafile Vector image
NCB Microsoft Developer Studio file
NIL Norton Icon Library file (EasyIcons-compatible)
NLU Norton Live Update E-Mail Trigger file
NSF Lotus Notes database
NST Noise Tracker music module (MOD) file
NTF Lotus Notes database template
NWS Microsoft OutlookExpress news message (MIME RFC822)


OBD Microsoft Office binder template
OBD Microsoft Office Binder
OBJ Object file
OBZ Microsoft Office Binder Wizard
OCX Microsoft Object Linking and Embedding custom control
OFN Microsoft Office FileNew file
OFT Microsoft Outlook template
OKT Oktalyzer music module (MOD) file
OLB OLE Object Library
OLE OLE object
OPT Microsoft Developer Studio file
ORG Lotus Organiser file
OR2 Lotus Organiser 2 file
OR3 Lotus Organiser 97 file
OSS Microsoft Office Search file
OST Microsoft Exchange Offline file
OTL Super NoteTab template file (Fookes)


P10 Tektronix Plot 10 drawing
P65 Pagemaker 6.5 file
P7C Digital ID file (MIME)
PAB Microsoft Personal Address Book
PAK Quake WAD file
PAL Windows colour palette
PAS Pascal source code (Borland)
PAT Corel Draw pattern
PCP Symantec Live Update Pro file
PBK Microsoft Phonebook
PBM Portable Bitmap
PCD Kodak Photo-CD image
PCD P-Code compiled test scripts as in Microsoft Tst and Microsoft Visual Test
PCL HP Laserjet bitmap
PCS PICS animation
PCT Macintosh PICT drawing
PCX ZSoft PC Paintbrush bitmap
PDF Adobe Acrobat Portable Document Format or Netware Printer Definition File
PDF Package Definition File from Microsoft Systems Management Server Verifies installed packages when performing an inventory scan of a client
PDQ Patton&Patton Flowcharting PDQ Lite file
PFA Type 1 font (ASCII)
PFB Type 1 font (binary)
PFC PF Component
PFM Printer Font Metrics
PGL HP Plotter drawing
PGM Portable Graymap (bitmap)
PIC PC Paint bitmap
PIC Lotus picture
PIC Macintosh PICT drawing
PICT Mac PICT image file
PIF Program Information File
PIF IBM PIF drawing
PIG Lucas Arts Dark Forces WAD file
PIN Epic Pinball data file
PIN Epic Pinball data file
PIX Inset Systems bitmap
PJ MKS Source Integrity file
PKG Microsoft Developer Studio application extension (similar to a DLL file)
PL Perl program
PLS MPEG PLayList file (used by WinAmp)
PLT HPGL Plotter drawing
PLT AutoCAD Plot drawing
PM5 Pagemaker 5.0 file
PM6 Pagemaker 6.0 file
PNG Portable Network Graphics bitmap
PNG Paint Shop Pro Browser catalogue
PNT MacPaint graphic file
PNTG Same as PNT file
POT Microsoft PowerPoint Template
PP4 Picture Publisher 4 bitmap
PPA Microsoft PowerPoint Add-in
PPM Portable Pixelmap bitmap
PPS Microsoft PowerPoint slide show
PPT Microsoft PowerPoint presentation
PRE Lotus Freelance presentation
PRF Windows system file
PRF Macromedia Director settings file
PRN Print Table (space delimited text)
PRS Harvard Graphics for Windows presentation
PRZ Lotus Freelance Graphics 97 file
PS Postscript Interpreted drawing
PSD Adobe Photoshop bitmap
PST Microsoft Outlook Personal Folder File
PTM Polytracker music module (MOD) file
PUB Ventura Publisher publication
PUB Microsoft Publisher document
PWD Microsoft Pocket Word document
PWZ Microsoft PowerPoint Wizard
PXL Microsoft Pocket Excel spreadsheet


QAD PF QuickArt Document
QBW QuickBooks for Windows file
QDT Quick Books data file from the Quicken UK Accountancy/Tax/Invoice program
QIC Microsoft Backup file
QIF QuickTime-related image (MIME)
QLB Quick Library
QRY Microsoft Query
QST Quake Spy Tab file
QT QuickTime Movie
QTI QuickTime-related image
QTIF QuickTime-related image
QTM QuickTime Movie
QTP QuickTime Preferences file
QTS Mac PICT image file
QTS QuickTime-related image
QTX QuickTime-related image
QXD Quark XPress file


R Pegasus Mail resource file
RA Real Audio sound
RAM Real Audio sound
RAR RAR compressed archive (Eugene Roshall's format)
RAS Sun Raster Images bitmap
RAW Raw File Format (bitmap)
RC Microsoft Visual C++ Resource Script
REC Recorder macro
REG Registration file
RES Microsoft Visual C++ Resource
RLE Run-Length Encoded bitmap
RM Real Audio video file
RMD Microsoft RegMaid document
RMF Rich Map Format (used by 3-D game editors to store a map)
RMI MIDI music
ROV Rescue Rover data file
RPT Microsoft Visual Basic Crystal Reports file
RTF Rich Text Format document
RTM Real Tracker music module (MOD) file
RTS RealAudio's RTSL document
RVP Microsoft Scan Configuration file (MIME)


SAM Ami Professional document
SAV Saved game file
SBK Creative Labs Soundfont 1.0 Bank file (Soundblaster)
SBL Shockwave Flash object
SCC Microsoft Source Safe file
SCD Matrix/Imapro SCODL slide image
SCD Microsoft Schedule+ 7
SCF Windows Explorer command file
SCH Microsoft Schedule+ 1
SCN trueSpace2 scene
SCP Dial-Up Networking Script
SCR Windows screensaver
SCR Fax image
SCT Scitex CT bitmap
SC2 Microsoft Schedule+ 7
SD2 Sound Designer 2 file
SDL SmartDraw library
SDR SmartDraw drawing
SDT SmartDraw template
SEA Self-expanding archive (used by Stuffit for Mac files and possibly by others)
SEP Tagged Image File Format (TIFF) bitmap
SES Cood Edit Session file (common digital audio editor file )
SFX RAR self-extracting archive
SF2 Creative Labs Soundfont 2.0 Bank file (Soundblaster)
SHB Corel Show presentation
SHB Document shortcut file
SHG Hotspot bitmap
SHS Shell scrap file
SHW Corel Show presentation
SIT Stuffit archive of Mac files
SKL Macromedia Director resource file
SL PACT's Save Layout extension
SLK Symbolic Link (SYLK) spreadsheet
SND NeXT sound
SND Mac Sound Resource
SQC Structured Query Language (SQR) common code file
SQR Structured Query Language (SQR) program file
STM Scream Tracker music module (MOD) file
STY Ventura Publisher style sheet
SVX Amiga 8SVX sound
SYS System file
SWA Shockwave audio file in Macromedia Director (an MP3 file)
SWF Shockwave Flash object
S3M Scream Tracker 3 music module (MOD) file


TAR Tape Archive
TAZ Unix Gzip/Tape Archive
TEX Texture file
TGA Targa bitmap
TGZ Unix Gzip/Tape Archive
THEME Windows 95 Desktop Theme
THN Graphics Workshop for Windows thumbnail
TIF Tag Image File Format (TIFF) bitmap
TIFF Tag Image File Format (TIFF) bitmap
TIG Tiger file, used by US government to distribute maps
TLB OLE Type Library
TMP Windows temporary file
TPL CakeWalk Audio Template file
TRM Terminal file
TRN MKS Source Integrity project usage log
TTF TrueType font
TWF TabWorks file
TWW Tagwrite Template
TXT Text
TZ Old compression format file
T2T Sonata CAD modelling software file


UDF Windows NT Uniqueness Database File
ULT Ultratracker music module (MOD) file
URL Internet shortcut
USE MKS Source Integrity file
UU UU-encoded file
UUE UU-encoded file


VBA VBase file
VBP Visual Basic Project
VBW Microsoft Visual Basic workspace
VBX Visual Basic custom control
VCE NMS, used by Cool Edit
VCF Vevi Configuration File; defines objects for use with Sense8's WorldToolKit
VDA Targa bitmap
VI Virtual Instrument file from National Instruments LABView product
VIR File identified as a virus-infected file by Norton AntiVirus and possibly others
VIV VivoActive Player Streaming Video file
VLB Corel Ventura Library
VOC Creative Labs Sound Blaster sound
VP Ventura Publisher publication
VQE Yamaha Sound-VQ Locator file
VQF Yamaha Sound-VQ file (possible emerging standard)
VQL Yamah Sound-VQ Locator file
VSD Visio drawing (flow chart or schematic)
VSL Download List file (GetRight)
VST Targa bitmap
VSW Visio Workspace file
VXD Microsoft Windows virtual device driver


WAB Microsoft Outlook file
WAD Large file for Doom game containing video, player level, and other information
WAV Windows Waveform sound
WB1 QuattroPro for Windows spreadsheet
WB2 QuattroPro for Windows spreadsheet
WBK Microsoft Word Backup
WBL Argo WebLoad II upload file
WCM WordPerfect Macro
WDB Microsoft Works database
WEB CorelXara Web document
WGP Wild Board Games data file
WID Ventura width table
WIL WinImage file
WIZ Microsoft Word Wizard
WK1 Lotus 123 versions 1 & 2 spreadsheet
WK3 Lotus 123 version 3 spreadsheet
WK4 Lotus 123 version 4 spreadsheet
WKS Lotus 123 Worksheet spreadsheet
WKS Microsoft Works document
WLF Argo WebLoad I upload file
WLL Microsoft Word Add-In
WMF Windows Metafile
WOW Grave Composer music module (MOD) file
WP WordPerfect document
WPW Novel PerfectWorks document
WP4 WordPerfect 4 document
WP5 WordPerfect 5 document
WP6 WordPerfect 6 document
WPD WordPerfect Demo
WPD WordPerfect Document
WPG WordPerfect Graphic
WPS Microsoft Works document
WPT WordPerfect Template
WQ1 QuattroPro/DOS spreadsheet
WQ2 QuattroPro/DOS version 5 spreadsheet
WRI Write document
WRL Virtual Reality model
WRZ Another VRML fileject
WS1 WordStar for Windows 1 document
WS2 WordStar for Windows 2 document
WS3 WordStar for Windows 3 document
WS4 WordStar for Windows 4 document
WS5 WordStar for Windows 5 document
WS6 WordStar for Windows 6 document
WS7 WordStar for Windows 7 document
WSD WordStar 2000 document
WVL Wavelet Compressed Bitmap
WWL Microsoft Word add-in file


XAR Corel Xara drawing
XBM A MIME 'xbitmap' image
XIF Wang imaging file (comes with Windows 95)
XLA Microsoft Excel add-in
XLB Microsoft Excel toolbar
XLC Microsoft Excel chart
XLD Microsoft Excel dialogue
XLK Microsoft Excel backup
XLL Microsoft Excel add-in file
XLM Microsoft Excel macro
XLS Microsoft Excel worksheet
XLT Microsoft Excel template
XLV Microsoft Excel VBA module
XLW Microsoft Excel workbook / workspace
XM FastTracker 2, Digital Tracker music module (MOD) file
XNK Microsoft Exchange shortcut file
XR1 Epic MegaGames Xargon data file
XTP XTree data file
XWF Yamaha XG Works file (MIDI sequencing)
XY3 XYWrite III document
XY4 XYWrite IV document
XYP XYWrite III Plus document
XYW XYWrite for Windows 4.0 document
X16 Macromedia Extra (program extension), 16 bit
X32 Macromedia Extra (program extension), 32 bit


YAL Arts & Letters clipart library
YBK Microsoft Encarta Yearbook


Z Unix Gzip Compressed
ZIP Zip file Compressed archive
ZOO An early compressed file format

Numbers and symbols

000-999 Used to number old (backup) versions of files (for example, CONFIG.SYS when changed by an installation program); also used to number related data files for multiple users of a small- scale PC application
12M Lotus 123 97 Smartmaster file
123 Lotus 123 97 file
2GR and 3GR VGA Graphics driver/configuration files under Windows
386 A file for use in an 80386 or higher microprocessor
669 Composer 669, Unis Composer music mod file
#01 and higher A method of numbering picture files for a roll of film that has been scanned for computer presentation
$$$ Used by OS/2 to keep track of archived files
@@@ Screen files used in the installation and instruction on use of such applications as Microsoft Codeview for C

Some thoughts on programs and techniques to try:

Perhaps the hardest part of opening an unknown document is having the patience to try often enough to succeed.  For most anything, you'll get off to a good start using the DataViz product, MacLinkPlus. This came freely for some time with Apple OS upgrades and System purchases, but the word on the street is that Apple wants to cut some of the cost off of their new models, so the freebie days of MacLinkPlus may be over. If you deal with a lot of unknown files, the commercial version is worth every cent... just for the document converter and translation filters. But you don't have to use this package, as your Mac likely has some pretty powerful software already on it (or available from the Internet), just waiting for you to ask in the right way for it to make your life easier.  Here are some thoughts on what programs we use routinely in our labs:

Text:   We always begin with SimpleText (or TeachText, if you are using pre-System 7.5 for the Mac).  This is such a powerful little program, and our Windows friends are still waiting for something similar to come out for their platform.  If the file is too big to be opened with SimpleText (and you have adjusted your RAM allocation), work from ClarisWorks or AppleWorks, NisusWriter, BBEdit, WordPerfect, or Microsoft Word.  MacWrite, PageMaker, InDesign, and Quark have all succeeded in unexpected ways for us in the past, too.

Spreadsheets:  Hands down, Excel still rules the spreadsheet world. But if your old 1-2-3 file comes out garbled, try opening from within ClarisWorks/AppleWorks. This rarely does the trick, as C/A-works will often confuse the file as a text document. Lotus once had some neat tricks of its own, but our in-house copy is too old to properly evaluate newer files with any reliability.  Lotus Notes may be another option.

Graphics:  Everyone has to deal with graphics, and with so many formats, there is only one way to sensibly start: with GraphicConverter. This shareware gem is worth the cost of a handful of Adobe products, but runs a heck of a lot less.  Download the demo, then send the programmer a check -- we think the world of GraphicConverter.  You may try these other avenues to view graphics: Photoshop, Canvas, Illustrator, FreeHand, ClarisWorks/AppleWorks, Quark, PageMaker, GIFconverter, JPEGviewer, MS Word, epsConverter, JPEGit, SimpleText, QuickTime Pictureviewer, or FileMaker Pro.

Databases:  Database files are as difficult to translate as spreadsheets. Always try to get the source file of the database sent to you in TAB or Comma-delimited (separated) form as a text export. Certain databases, such as MSAccess and AlphaFive are unnecessarily difficult to use. As a result, users of these databases typically think they are destined to be stuck with the program forever. Not true, provided you can export your data.  Even relatively simple database engines such as ClarisWorks/AppleWorks or FoxPro can often import the exported files.  More powerful databases like FileMaker Pro and 4D can make significant improvements to the ability for a user or firm to tailor imported information without being tied to a database "guru". All the same, opening databases is a tricky business at best when you don't know where you are starting from... often, hiring a professional is the best economic solution in this case.

Multimedia (Sound and Vision): There are dozens of shareware and commercial multimedia packages available foropening and viewing these kind of files, from Apple's SimpleSound and Windows Media Player to QuickTime Pro.  Search the web for these kinds of files using Sherlock (OS 8.5 and above) or the search engines listed on our Links page.

Legacy systems: In geek-speak, these are older computers or operating systems.  Perhaps the best-known example is MS-DOS and Windows 3.1.  DOS used a convention called 8.3, where file names could not be any longer than eight characters in length, and were followed by an extension like the ones listed above to identify what kind of file it was.  An example is DOCUMENT.TXT , such as we used in the above reference table.  This would be a text document.  If a Mac user, who was comfortable using their 30-plus character names, gave an ASCII text document to a DOS user, often the file could not be read because the DOS or Windows system didn't know what to do with the file.  An example would be a file called PAULSRESUME.DOC.  This file would fail to be read by a word processor on primative operating systems because the DOS system would see the file as PAULSRES.UME. DOS wouldn't have a clue what a ".UME" file was.  You would have to rename the file as PAULSRES.DOC, then attempt to open it.

Keep in mind, these headaches still persist in Win 95 and later versions.  Recently, I emailed a friend an Acrobat file called PICTURE.  As with many email's, it was compressed to PICTURE.SIT before I sent it.  My Internet browser was set up to automatically convert the file to a Binhex format (for Unix computers to handle it properly) to become PICTURE.SIT.HQX -- which is how it arrived on my friend's computer.  The recipient knew she had to decode the file from HQX, and received the PICTURE.SIT file.  This was promptly decompressed to PICTURE.  However, the file still could not be opened as her system could not properly recognize that it was a PDF file, even when she attempted to open the file from within Acrobat reader.  An errant message popped up stating that the file did not begin with %pdf.  The solution was simple: add the proper extension to the back of the file (rename the file to PICTURE.PDF) and the file opened flawlessly with a double-click in Windows.  My mistake was not to add the .PDF to the end of the file prior to sending it.  Lesson?  Never assume anything will work on a Windows machine unless you give it explicit instructions.

Time and again, we've seen where a Mac could open a document thought completely dead from PC-formatted floppies, or even from PC floppies horribly infected with the Windows virus-of-the-week.  If you work in a mixed-platform environment, take advantage of the special skills your Mac can offer your Windows brethren.  File management is far easier on a Mac -- if you know the right tools to help you with your work or play.