Filename Extensions List
So you see a file somewhere on the 'net with a
name like "greatfile.xyz" and you would like to
download it and use it on your computer. Will it work? What
does the file extension xyz mean, anyway? This handy
guide attempts to provide answers to those questions.
It is not meant to be read straight through;
rather, it is meant to be a reference. An extension may be
looked up either with the "find in page" option of your
browser or by appending a "#xyz" (without the quotes
and with xyz replaced by the extension in question)
to the "go to" or "URL" field on your browser. There is also
a Search
Interface that will return not only the specific
extension sought but also other entries that reference it. Be
aware though that it assumes familiarity with the computer
basics discussed on the terms
page.
You may notice that most extensions are three
letters (or fewer) long. This is due to a historical
limitation of the operating system called CP/M (that was later inherited by
MS-DOS). In fact, the whole
concept of file extensions comes from CP/M. Most modern operating
systems do not attribute any special meaning to the "."
(period, or dot) character.
Be aware though that there is no standardization to
filename extension usage, and many different people
have used extensions to apply to many different things. This
list only attempts to provide likely guesses of what
something is apt to be. Programs that can make use of many of
these extensions can be found on the Guide to
Free Software.
If you want something added or see a problem
with something already here (but keep in mind this guide is
not meant to be overly technical) please send .
-
3dt
-
A Firebird database file holding a 3D representation of information usable by an organizational software application called Topicscape.
It is ASCII and can only be used on machines with both Firebird and Topicscape.
-
a
-
An archived library of object files that can be used in the process of building programs. The generic extension lib is also sometimes used this way.
-
abw
-
An AbiWord word
processing document; it can be read on any machine
with AbiWord installed (available for
WinTel boxes,
Mac OS X,
BeOS, and most
UNIXes for free).
-
adf
-
The Amiga disk
file stores the contents of an entire
Amiga
floppy in a single
file. It is
binary, but
is designed to work on any machine that has Amiga
emulator
software (Amiga emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the Amiga itself.
-
afm
-
The Adobe Font
Metric file is used to provide
information on Adobe
fonts. It is
in simple ASCII.
-
ai
-
An Adobe Illustrator
document. It is binary
but will work directly on any machine that has Adobe
Illustrator.
-
aiff & aif
-
The audio interchange
file format originated
on Macs but has since been
ported to several other platforms as well.
-
apd
-
An Aldus
PageMaker
document. It is
binary but will
work directly on any machine that has Aldus PageMaker.
-
arc & ark
-
A file that has been compressed with the arc
program or similar will
get the "arc" (and very rarely the "ark") extension. Its
performance is somewhat less than gzip
& zip, but decompression programs
exist on virtually every platform. Like zip, arc does
not require a separate tarring step;
it uses its own method to do the equivalent.
-
arj
-
Similar in all respects to arc,
but a different method of
compression
was used. Programs
to uncompress this type of file do not exist on as many
platforms as they
do for the original arc.
-
art
-
An image format
(typically called the Johnson-Grace format) with extremely aggressive
compression at the expense of
quality. This format is most frequently seen by AOL users
as AOL automatically compresses online images of other
formats (like gif or
jpeg) into
Johnson-Grace images. This is why AOL users often do not see web pages
at the same quality level as other people, often seeing blurry images
where others see clear images (and occasionally even seeing
black bars that are not really present in images).
-
asp
-
A proprietary solution that performs more or less like shtml.
-
au
-
An audio format
that originated on UNIX systems
but has since been ported to
virtually every other platform
out there from the Newton
on up. Note though that these files can be either stereo or mono; stereo is
not supported on as many machines as mono.
-
avi
-
A video
file will
typically store a movie clip. It's generally supported by many different
platforms, although
note that there are several different versions of AVI files in use,
and not all players will play all versions.
-
awk
-
Probably an AWK script;
it can be made to run on any machine that has
awk.
-
B1
-
A compressed format similar to GZip but favoring speed over compression ratio. In particular, it will detect many file types that are already compressed and skip processing them to save time. It is an open format, and free applications and libraries exist to process it.
-
bar
-
The bar format is
similar in concept to the tar
format, but is not found on as many computer systems.
-
bat
-
A file with this extension is most likely a
batch file for either
CP/M or
MS-DOS and is
not likely to work on a different
platform than the one for
which it was originally written. It should be simple
ASCII however, so it might
be possible to figure out what it is supposed to do and
write a new script to do
the same.
-
bdf
-
The Bitmap Distribution
Format is a
format for storing
bitmapped
fonts. It is in simple
ASCII. It originated on the
X-Windows system but can
be made to work on other systems as well. It is a product
of Adobe.
-
bep
-
A file that has been compressed with
geoBEAP. It can be used
on GEOS systems that have geoBEAP
installed.
-
blb & blorb
-
A single interactive fiction title may require numerous parts, including images, sounds, music, and of course an executable. A Blorb file simply packages them all together in a standardized way that can be recognized by most interactive fiction interpreters.
-
bmp
-
Microsoft
bitmap
image format. This is a
fairly simple bitmap
format that can be viewed on many different
platforms
but is directly supported by very few
browsers. It is not
used too much on the web
(fortunately, as it is very inefficient) with
GIFs,
JPEGs,
PNGs, and even
X-bitmaps
being preferred as they are much more
portable. It is somewhat
similar to the pict format.
-
bsh
-
Probably either a Bourne
Shell
script or a
Bourne-Again Shell script. These are both pretty similar to each other,
anyway (Bourne-Again is a superset of Bourne), and the
Bourne-Again Shell is available for many different
platforms.
-
bz2
-
The bzip2 compression
program is similar in
nature to both gzip and
zip. It will often outperform
the other two, but it is not yet particularly widespread and so is not
usually the best choice for information that must be
shared between different platforms.
-
c
-
A source file written in the C
programming
language. It should be in
simple ASCII and
(depending upon how portably
it was written) should be usable on any machine with a C
compiler. There is a good
chance though that it will also require (at minimum) some
h files.
-
C , cpp , & cxx
-
A source file written in the C++
programming
language. It should be in
simple ASCII and
(depending upon how portably
it was written) should be usable on any machine with a C++
compiler. There is a good
chance though that it will also require (at minimum) some
H
(or even h) files.
-
cgi
-
A common gateway
interface file is a
program designed to be
run over the
web. It is really something else in
disguise, like a Perl script,
an AWK script, a
Bourne Shell
script, a Java
program, or whatever.
-
cgm & metafile
-
A computer graphics
metafile is an image
file.
Programs for handling metafiles
can be obtained for most platforms.
-
chr
-
This is a rather generic sort of extension indicating
"character" data; of particular note though is the fact
that Borland has a WinTel-only
font
format that uses this extension.
-
com
-
A command file is a
program for a
CP/M,
MS-DOS,
MS-Windows, or possibly even
an x86
GEOS machine. It will probably not
work on a platform other than the one for which it was
designed (including the different variants of
MS-Windows). Similar to, but usually smaller than, an exe file.
-
cpt
-
A file that has been compressed with the Compact Pro program will get the "cpt" extension.
A less likely possibility is a special type of Zope Page Template called a Controller Page Template that is used for generating online forms.
-
crt
-
There are two types of unrelated files that use this suffix. The more common type is designed to hold certificates used to authenticate resources sent over the Internet; the less common type is a UNIX crontab file used to schedule automatic repeating tasks.
-
csh
-
Probably a C-Shell script.
This will probably be difficult to make work on
non-UNIX
systems, but it will at least be in simple
ASCII so it
might be possible to figure out what it is doing and
rewrite it.
-
css
-
A cascading style
sheet file is used to define a
cascading style sheet for a
web page. The purpose is to
provide more control over the
fonts, colors, layout,
etc. that go into the web page than could be provided by raw
HTML. Also, since the
cascading style sheet file is separate from the HTML files, it can be
shared (or even inherited; a little outside the scope of
this document) by multiple web pages to help provide a
consistent look-and-feel across a web site. It is not yet
fully supported by all
browsers;
newer versions of all popular browsers do provide some CSS support, however.
-
cvt
-
GEOS
files have external resources
associated with them; files with this extension are
typically packaged from a GEOS environment for
transmission.
-
cwk
-
A ClarisWorks (or AppleWorks) document (can be a
word processing, spreadsheet,
database, presentation
program, drawing program, etc. document); can be read on
any machine with ClarisWorks installed (available only
for WinTel boxes and Macs, but usually not for free).
-
cwl
-
A ClarisWorks (or AppleWorks) library can be read on
any machine with ClarisWorks installed (available only
for WinTel boxes and Macs, but usually not for free).
There are some minor differences though that will sometimes cause a library written with a particular version of ClarisWorks (or AppleWorks) to be read-only if used with a different version.
-
cws
-
Pretty much like a cwk file, but
indicates stationery rather than an ordinary document.
-
d00 - d99
-
This file is designed to work on any machine that has C64
emulator
software (C64 emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the C64 (or C128) itself. It is essentially
a repackaging of a regular Commodore
delta file.
-
d64
-
The C64 disk
file stores the contents of an entire
C64
floppy in a single
file. It is
binary, but
is designed to work on any machine that has C64
emulator
software (C64 emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the C64 (or C128) itself.
-
del
-
A delta file used (rarely) by
C64 or C128 computers
for data storage. Delta files are identical to the much more common
sequential data file,
differing only in name. Sometimes these are referred to as "deleted"
files, but this is not a particularly good term as delta files can perform
active duty and have nothing to do with deletion.
-
dir
-
Some systems use the "dir" extension for directories or folders.
-
dmf
-
The DMF format
is used for storing vector
fonts. It originated
on Amiga systems
and will not work on most other machines without conversion.
-
dmg
-
A
dmg file is a Mac OS disk image that can be mounted as if it were a hardware disk.
-
doc
-
This is a rather generic sort of extension indicating
some sort of document, usually in simple
ASCII; of particular note though
is the fact that both old versions of FrameMaker and MS-Word often save
their native format
files with this extension, and such a file may only be
read with FrameMaker or FrameViewer (if a Frame document)
or MS-Word (if an MS-Word document). Neither of these
programs are available for all
platforms, and even when they
are available are usually not free. To complicate matters
even further, there are several different versions of
MS-Word in common use that cannot reliably read each others'
files. Thus in general this format should not be viewed
as portable, and
chances of reading it on any particular platform are
slim. Note that newer versions of FrameMaker save documents with the FM extension and Microsoft is splitting its MS-Word format into two variants that use either the DOCX or the DOCM extension. Documents saved from either FrameMaker or MS-Word
that are meant for other machines should probably be
saved in MIF or
RTF
formats (respectively) in any case.
-
docm
-
This extension is used by one of Microsoft's replacements for the DOC format. It can only be read by machines with MS-Word (at least version 12) installed. Note that unlike the DOCX variant, these files can contain embedded code (the "m" stands for "macro") and should thus not be considered safe if they come from untrusted sources.
-
docx
-
This extension is used by one of Microsoft's replacements for the DOC format. It can only be read by machines with MS-Word (at least version 12) installed. It is a safer sibling to the DOCM format.
-
dtml
-
A DTML file with dynamic extensions
that provide for dynamic capabilities. DTML files are
often used with Python files in
implementing dynamic web sites.
-
dwf
-
The DEC Windows
Format is a
format for storing
bitmapped
fonts that originated on DEC
UNIX systems and will not
work on most other machines without conversion. It is a
product of the company PageStream.
-
egg
-
Python Egg files are similar to JAR files but for Python
rather than Java.
-
el
-
An Emacs
LISP
file is used to extend
the capabilities of the popular Emacs editor. It is
ASCII and will work on
any machine with Emacs installed.
-
elc
-
A Emacs
LISP
file (compiled)
is used to extend the capabilities of the popular Emacs editor. It is
a binary,
compiled version of a
.el file.
-
emf
-
An MS-Windows
enhanced metafile is
like an ordinary CGM metafile but with
extensions that make it specific to MS-Windows, and it
will not work on most other machines without conversion.
-
eps
-
An encapsulated
Postscript
file is often a combination of
Postscript and various miscellaneous image file
formats and is often difficult
to use on a set up that is different from the one on
which it was created.
-
etd
-
An Adobe e-book
download
file is not an e-book itself but
rather a series of instructions that a computer will be
able to use to download an e-book and load it into an
e-book reader. It is binary
and not particularly portable.
-
exe
-
An executable is a
program for a
CP/M,
MS-DOS,
MS-Windows, or possibly even
an x86
GEOS machine. It will probably not
work on a platform other than the one for which it was
designed (including the different variants of
MS-Windows). Similar to, but usually larger than, a com file.
-
f3 & f3b
-
The Sun Folio
format is used for storing
vector
fonts. It originated on Sun
UNIX systems but will work on
many X-Windows
systems.
-
f66 , f77 , & f90
-
A source file written in the ForTran
programming
language. It should be in
simple ASCII and
(depending upon how portably it was written)
should be usable on any machine with a ForTran
compiler. The only caution is
that the number refers to the version of ForTran used.
-
faq
-
A FAQ file is
traditionally a simple ASCII
document that attempts to answer frequently asked questions.
-
fes
-
A format exported by an organizational software application called Topicscape.
It is in simple ASCII and can thus be viewed on pretty much any machine, although it can only be usefully imported into Topicscape.
-
fla
-
A Macromedia Flash source document. Can be used with any
machine that has the commercial Macromedia Flash editor,
currently available for only
Macintosh and
MS-Windows.
-
fm
-
This indicates a FrameMaker native
format document. Such a file may
only be read with FrameMaker or FrameViewer or similar
(currently only available for a price on
UNIX,
Mac, &
WinTel
platforms).
-
fnc
-
This file is a Frogans Network Certificate. It is a small file used to permit the initialization of a Frogans network.
-
fpx
-
The
FlashPix
image format was
developed by Kodak but is now governed by an independent
organization called the Digital Imaging Group.
Programs for viewing this
format are available for a few different
platforms. An extended version
of this format can also handle audio, but this variant is
not too widely supported at this time.
-
ftk
-
The IBM Triton
FastTrack
format is an audio
format. It is not too widely recognized.
-
gam
-
A TADS (Text Adventure Development System) data file.
Typically it will represent an interactive fiction story
(or interactive tutorial, or similar). It is
binary but will work on any
machine with some flavor of TADS interpreter, and such
interpreters are available for several different
platforms, usually for free.
It is currently not as
portable as a
Z-machine file.
-
gblorb & glb
-
A Blorb file designed to work within a Glulx virtual machine.
-
gdf
-
A GEOS dictionary
file. It is (obviously) meant to be used with
GEOS.
-
ged
-
This file is used for holding genealogy data, and is most typically called a GedCom file (short for genealogy data communications). Most software applications made for performing genealogy work (or even just basic family trees) are capable of working with GedCom files and they can generally be used on all platforms. Note however that some companies have made proprietary extensions to the GedCom format, so transfers from one software application to another are not completely guaranteed to be safe.
-
geo
-
A GeoWorks document; it can be used on any machine with
GeoWorks installed (which in turn requires
GEOS).
-
gf
-
The Generic Font format is used to store
font information. It will
work on any machine that has TEX installed.
-
gif
-
A general image
format file is a representation of an
image or simple animation. The
format was created by
Compuserve and is copyrighted. It is currently the most widely
accepted image format in existence, but the concern over
its copyright has inspired many people to try and move
away from its use. Some popular alternatives include JPEGs,
PNGs, and X-bitmaps for still images and
MPEGs and
QuickTime movies
for animations. A GIF can only contain two-hundred
fifty-six different colors, of which "transparent" is an
allowed color. Each GIF can use its own set of 256
colors, though.
-
graffle
-
An OmniGraffle file is a type of XML format. It is used to hold charts and diagrams.
-
gz & z
-
The GNU Zip program is
used to compress the
size of a single file. If more than one file has to be
compressed, they must be tarred
together first. The program that does the compression is
called gzip, and the gzipped file cannot be used until it
has been gunzipped. The gzip program has its origins on
UNIX machines, but it has
been ported to most other
computer types as well and is typically available for
free under the terms of the GNU public license. The "gz"
form is preferred; the other is considered obsolete as it
was frequently confused with the output of the UNIX compress program and deliberately changed
to be something more distinctive. Gzip is better at
compression than compress.
-
h
-
A header file written in either the C,
C++,
Objective-C,
Objective-C++,
or Inform
programming
language. It should be in
simple ASCII and
(depending upon how portably it was written)
should be usable on any machine with a C (or C++, ObjC, or ObjC++ as
appropriate) compiler.
Typically it would be used in conjunction with a
c or
C file.
-
H , hpp , & hxx
-
A header file written in the C++
programming
language. It should be in
simple ASCII and
(depending upon how portably
it was written) should be usable on any machine with a C++
compiler. Typically it would
be used in conjunction with a C file.
Note that the h extension is also
sometimes used for C++ header files.
-
hdf
-
The hierarchical data
format supports the storage of many
different data types, including images and tables. Tools
for using HDFs are available for most higher-end
machines, including most UNIX
systems, Macs with a
PowerPC
processor, and
Windows NT &
Windows '95 systems that
possess at least a Pentium processor. There is
also a Java interface for
handling HDFs.
-
hex
-
This is a generic sort of extension indicating some sort
of hexadecimal (or even binary)
data; of particular note
though is that interactive
fiction data files for
use with the Hugo program typically use this extension.
-
hqx
-
This indicates a BinHex file. It is similar in theory to
a uuencoded file, but
was developed originally for the
Macintosh. Today decoders can be
found for MS-Windows,
MS-DOS, and
UNIX in addition to the Mac.
-
htc
-
An HTML Component file is a proprietary way of encapsulating a particular behavior to be attached to a web page. It can always be replaced with standard HTML, CSS, and JavaScript.
-
html & htm
-
A hypertext
markup language file
contains hypertext
capable of being read and interpreted by a
browser. The bulk of the world wide web is in HTML
format.
-
ics
-
A file with this extension normally contains calendar information. It should be in simple ASCII
and should be usable on any machine with software that supports the iCalendar
standard.
-
iff
-
The image file
format was originally created for the Amiga but can now be read by
numerous different image manipulation
programs for several different
platforms.
-
indd
-
This indicates an Adobe InDesign native
format document. Such a file may
only be read with InDesign
(currently only available for a price on
Mac &
WinTel
platforms).
-
indt
-
This indicates an Adobe InDesign native
format template. Such a file may
only be read with InDesign
(currently only available for a price on
Mac &
WinTel
platforms).
-
inf
-
A source file written in the Inform language (a language
optimized for creating interactive
fiction). Inform compilers
have been ported to virtually every
platform in use today,
and will create either Z-machine code
or Glulx code depending upon the
specifics of the compiler.
-
jar
-
A Java
archive should be usable on any machine
with Java.
-
java
-
A file with this extension
should be a file written in the Java
programming language. It should be in
simple ASCII (although
also possibly Unicode)
and should be usable on any machine with a Java
compiler.
-
jbig & jbg
-
An image format
developed by the Joint
Bi-level Image Experts
Group. It is optimized for FAX type
images, and has absolutely nothing to do with either JPEG or
MPEG in
spite of the similarity of names. It is
lossless and free viewing
programs are available for
it for most platforms,
but it is not directly recognized by most
browsers.
-
jhtml
-
Very similar to shtml but utilizes
Java to do its work.
-
jpeg & jpg
-
An image format
optimized for "natural" images developed by the
Joint Photographic
Experts Group, JPEGs
are probably second only to GIFs in
level of acceptance. JPEGs manage to capture wonderfully
detailed images in millions of colors in minimal space by
taking advantage of limitations with human vision, and
performing little lossy
compressions. This
means that each time a JPEG is saved, it will lose a
little more quality, although each individual loss will
be nearly invisible to the human eye. If care is not
taken, however, a JPEG image can become worse looking
than a color-limited GIF. JPEGs are also not good at
storing cartoon-like images or line drawings; for these
cases either GIFs or PNGs or
X-bitmaps are better choices. JPEGs also
cannot contain a transparent color. If a transparent
color is needed, GIFs, PNGs, and X-bitmaps are better
choices. JPEG has nothing to do with either
JBIG or
MPEG in spite of
the similarity of names.
-
js
-
A file with this extension
is probably written in the JavaScript
programming
language for
browsers. It should be in
simple ASCII and should
be usable on any machine with a browser that supports
JavaScript. Note that there is no relationship between
JavaScript and Java; it is an
unfortunate coincidence of names.
-
key
-
An Apple Keynote document. It is a compound document built from XML files (and various types of media files) and will work on any machine that has Apple Keynote installed.
-
koa
-
Usually a Koala Paint file; an
image format originally designed for
the Commodore 64,
but readable by many other machines as well with the
appropriate software.
-
kon
-
This is most likely part of a Yahoo! (formerly Konfabulator) Widget. It will be simple ASCII
typically containing a mix of XML and JavaScript.
-
kpf
-
A Komodo Project File contains XML data that defines a project for use with the Komodo software development tools.
-
ksh
-
Probably a Korn Shell script. It
should work on most machines that have a working Korn Shell. It can usually
also be made to work under the Bourne-Again Shell with
only minor modifications.
-
kth
-
An Apple Keynote theme file. It is an XML format and will work on any machine that has Apple Keynote installed.
-
ldb
-
A Microsoft database lock file is an indicator that the corresponding
MDB file is currently locked and should not be edited.
-
lha
-
A lharc file is similar in all respects to an
arc file, but a
different method of compression
was used. Programs to uncompress
this type of file do not exist on as many
platforms as they do for arc.
-
lib
-
This is a generic sort of extension indicating "library"
data; of particular note though is that native
Amiga
font files often use this
extension.
-
lit
-
This indicates a Microsoft Reader
e-book. It is currently only known
to work with some (although not all) flavors of
MS-Windows (including Windows CE), and is
binary in nature.
-
lnx
-
A LYNX file is similar in all respects to an
arc file, but a
different method of compression
was used. Programs to uncompress
this type of file do not exist on as many
platforms as they do for arc.
-
ltf
-
This file is a Frogans short-cut (or link to Frogans). It is used to indicate a Frogans URL on the Internet. It can only be opened with a Frogans player.
-
lwf
-
An image format designed
to minimize file size while maintaining image quality.
LWFs can utilize both lossy
and lossless compressions.
Typically they will be better compressed than the equivalent
JPEGs if the lossy form is
utilized. As of this writing, virtually no browsers have the built-in
support to handle LWFs, but separate
plug-ins are available for
many.
-
M & mm
-
A source file written in the Objective-C++
programming
language. It should be in
simple ASCII and
(depending upon how portably
it was written) should be usable on any machine with an Objective-C++
compiler. There is a good
chance though that it will also require (at minimum) some
H
or (h) files.
-
m
-
A source file written in the Objective-C
programming
language. It should be in
simple ASCII and
(depending upon how portably
it was written) should be usable on any machine with an Objective-C
compiler. There is a good
chance though that it will also require (at minimum) some
h files.
-
m4b
-
This is most likely an MPEG-4 container specialized for audio books. It's basically the same as an
mp4 file but with additional features (such as bookmarks) convenient for audio books.
-
mdb
-
A Microsoft database file is a binary file containing a database for use with Microsoft Access. It is not portable and in fact it requires specialty tools to extract the data.
-
mf
-
The MetaFont
format is used to store
font information. It will work on
any machine that has TEX
installed.
-
midi & mid
-
A musical instrument
digital interface file
is an audio file that will possibly work with any device
that is MIDI aware. MIDI is in some respects similar to
MOD, but it is
supported on far more dedicated musical devices but far
fewer computers.
-
mif
-
A Maker interchange
format file
is a Framemaker file with an
advertised format so
that it can be imported into other
desktop publishing or
word processing
programs. The ability
to handle MIFs is built into better word processors and
desktop publishers. It will behave the same across
different platforms.
-
miff
-
An image format used
with both the ImageMagick and GraphicsMagick suites of image processing
programs. It can be used on any
platform that supports either
ImageMagick or GraphicsMagick.
-
mng
-
A multiple-image network graphics file is used for storing animations. It is binary and related to the
png format.
-
mod
-
The audio module file originated on the
Amiga and takes the
approach of defining different instruments and then
describing what each does. It is fairly space-efficient,
and free software to play MODs is available for
WinTel boxes,
Macintoshes,
UNIX boxes, and even
Commodore 128s in
addition to the original Amiga.
-
mov & qt
-
A QuickTime
movie can actually be used to store both
movies and sounds. A file with this extension could thus
be either an audio file or a movie file. Both types are
supported by many different
platforms. Note
though that there are several different versions of QuickTime files
in use, and not all players will play all versions.
-
mpeg , mpg , mpeg2 , mpeg3 , mpeg4 , mp2 , mp3 , mp4 , m3u , & m4u
-
The Moving Pictures
Expert Group devised formats for storing both
movies and sounds. A file with this extension could thus
be either an audio file or a movie file. Both types are
supported by many different
platforms, with
perhaps the audio type being a little more recognized. Both types
also utilize lossy compression that is
designed to take advantage of the limitations of human
vision and hearing. Regardless the compression still
occasionally does weird things producing "MPEG
compression funnies", particularly during periods of
rapid movement in video. MPEGs are not limited to
computers; some digital satellite television
transmissions use an MPEG format, and DVDs use an MPEG
format. MPEG has nothing to do with either
JPEG or
JBIG in spite of
the similarity of names. MPEG does have some relation to
QuickTime, though, and
the next version of each will work to merge the two. If there is a number
at the end of the extension, it refers to the specific
generation of the MPEG format in use within the file.
-
nbk
-
Probably a Newton
backup. It is binary and not
particularly portable,
as in fact it could have been written by any one of a few different programs
(such as Newton Connection Utilities or Newton Backup Utility on either
Mac or
MS-Windows) which are not
guaranteed to work with the files generated by each other.
-
numbers
-
An Apple Numbers document. It is a compound document built from XML files (and various types of media files) and will work on any machine that has Apple Numbers installed.
-
o & obj
-
A relocatable object file is the result of compiling a source file in any of several programming
languages. It will be binary and will not be portable, and will not be runnable until it has been linked.
-
odb
-
An OpenDocument database file is the database
format portion of the OASIS OpenDocument standard. It is usable by many different database applications.
-
odc
-
An OpenDocument chart file is a format used for storing chart data and is part of the OASIS OpenDocument standard. It is usable by many different applications.
-
odf
-
An OpenDocument formula file is a format used for storing mathematical data and is part of the OASIS OpenDocument standard. It is usable by many different applications.
-
odg & otg
-
An OpenDocument graphics file is the drawing
format portion of the OASIS OpenDocument standard. It is usable by many different drawing applications. The version with the
"d" is an ordinary document; the version with the "t" is
a template for building other documents.
-
odi
-
An OpenDocument image file is a format used for storing image data and is part of the OASIS OpenDocument standard. It is usable by many different applications.
-
odp & otp
-
An OpenDocument presentation file is the presentation
format portion of the OASIS OpenDocument standard. It is usable by many different presentation applications. The version with the
"d" is an ordinary document; the version with the "t" is
a template for building other documents.
-
ods & ots
-
An OpenDocument spreadsheet file is the spreadsheet
format portion of the OASIS OpenDocument standard. It is usable by many different spreadsheet applications. The version with the
"d" is an ordinary document; the version with the "t" is
a template for building other documents.
-
odt & ott
-
An OpenDocument text file is the word-processing
format portion of the OASIS OpenDocument standard. It is usable by many different word-processing applications. The version with the
"d" is an ordinary document; the version with the "t" is
a template for building other documents.
-
oga & ogg
-
The Ogg Vorbis format is
an advanced binary audio
format similar to (but more capable than) the
mp3 format. It is patent and royalty free, and
is supported on most platforms.
-
ogv
-
The Ogg Theora format is
an advanced binary video
format that is patent and royalty free, and
is supported on most platforms.
-
opf
-
An open e-book package
will use this extension. It is binary,
but applications to read it
exist or are being developed for a number of different platforms.
-
p00 - p99
-
This file is designed to work on any machine that has C64
emulator
software (C64 emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the C64 (or C128) itself. It is essentially
a repackaging of a regular Commodore
program file.
-
pages
-
An Apple Pages document. It is a compound document built from XML files (and various types of media files) and will work on any machine that has Apple Pages installed.
-
pas
-
A source file written in the Pascal
programming
language. It should be in
simple ASCII and
(depending upon how portably
it was written) should be usable on any machine with a Pascal
compiler.
-
pbm
-
The portable
bitmap
format is an
ASCII image format designed
primarily to be portable
across different platforms.
It is not particularly space efficient, but can be handled by many
different image manipulation programs.
It is similar to pgm but can only
handle monochrome images. There is also a
binary variant that is more
space efficient but less portable.
-
pcf
-
The Portable Compiled
Format is a
format for storing
bitmapped
fonts. It is
binary, but still designed to be
portable. It originated on
the X-Windows system
but can be made to work on other systems as well.
-
pdb & prc
-
Probably a Palm package of
some type, either a Palm Database or a Palm Resource. In
either case, it is basically a
program made to run on the Palm
platform, and will
sometimes be a Palm DOC
type of e-book. It is binary and not particularly
portable, but
applications exist to read
Palm DOCs on a few other platforms.
-
pdd
-
The PhotoDeluxe
Data image
format was developed by Adobe
for use with its PhotoDeluxe
program and can be read by any
machine that has it installed (it is only available for
Macs and
WinTel boxes, and then generally
not for free).
-
pdf
-
The Portable Document
Format is a
format for storing all manner of
documents. PDF documents can contain sounds and
animations in addition to simple images and are
binary in nature. PDFs are also
fully capable of containing hypertext,
but unlike HTML will guarantee proper
printout. It is a product of Adobe and free PDF
interpreters are available for most machine types. There
are also free PDF plug-ins
available for Netscape and compatible
browsers.
-
pfa
-
The PostScript Font
ASCII is a format
for storing vector
fonts. It is simple
ASCII and originated on the
X-Windows system. It is
a creation of Adobe and the ASCII counterpart to the less
widely recognized PFB.
-
pfb
-
The PostScript Font
Binary is a format
for storing vector
fonts. It is
binary but designed to be
portable. It originated on
the X-Windows system.
It is a creation of Adobe and the binary counterpart to
PFA.
-
pfm
-
The Printer Font
Metric file is used to provide
font information on an MS-Windows
machine. It probably will not be useful anywhere else.
-
pgm
-
The portable
graymap
format is an
ASCII image format designed
primarily to be portable across
different platforms. It is not
particularly space efficient, but can be handled by many
different image manipulation programs.
It is similar to ppm but can only
handle shades of gray. There is also a
binary
variant that is more space efficient but less portable.
-
php , php3 , & php4
-
Very similar to shtml but utilizes
PHP to do its work.
-
phtml
-
Very similar to shtml but utilizes
Perl to do its work.
-
pict , pct , & pic
-
Macintosh
bitmap picture
format. This is a fairly
simple bitmap format
that can be viewed on many different
platforms but is directly
supported by very few browsers.
It is not used too much on the
web with
GIFs,
JPEGs,
PNGs, and even
X-bitmaps
being preferred. It is somewhat similar to the
bmp format, although utilizes
compression and so boasts
smaller file sizes.
-
pif
-
This extension can be used for more than one thing. First is the process interchange format, a temporary file used to facilitate communication between different programs.
There is also a rarely seen picture interchange format which can be used to store images. These two formats are both binary but can be used on pretty much any platform that has the appropriate support.
The third possibility is a Microsoft program information file; it can be used only on MS-Windows machines and is in reality just what is more commonly called an alias, link, or shortcut.
-
pk & pxl
-
The TEX
Packed
font
format is used for storing
bitmapped
fonts. It is
binary but will work directly on
any machine that has TEX. The PXL form is obsolete; all
current files should be PK.
-
pkg
-
Possibly a Newton
package of some type; a program
made to run on the Newton
platform. It
will frequently be a Newton book
type of e-book or a
Newton Script program. It
is binary and not
particularly portable,
but applications
have been written to read Newton books on a few other
platforms. Note that somewhat unfortunately, this
extension is also used for the unrelated (and now more common) Apple package
format used on
Macs.
-
pl
-
This extension will typically mean one of two completely
different things. The more common is a Perl
script, a
program written in the Perl
language. It should
run on any machine that has
Perl installed and is simple ASCII.
The second is a TEX Property
List file. It is used to provide information on
fonts. It is also simple
ASCII, so it should not be too hard to tell the two apart.
-
pm , pm3 , pm4 , & pm5
-
An Adobe PageMaker
document. It is binary
but will work directly on any machine that has Adobe
PageMaker (currently only available for
Macs and
WinTel boxes).
-
png
-
The portable network
graphics image
format is designed to replace
the GIF. In fact, PNG is sometimes
jokingly said to really stand for "PNG's not GIF". PNG is
completely lossless
and can handle millions of colors; it is not limited to a
palette of two-hundred fifty-six like GIF. It also has
full support for transparent colors. Its only real
disadvantage is that right now not all
browsers support
it directly. It has been recommended by the
W3C, though, so odds
are pretty good that most (if not all) future versions of browsers
will provide direct inline support for PNG, and PNG
images will start to become more commonplace on the web.
-
pov
-
POV-Ray source files will typically be
given this extension. POV-Ray source files are simple ASCII and should be readable
on most platforms.
Effective use can only be made of them on machines with
POV-Ray, however.
-
ppm
-
The portable
pixmap
format is an
ASCII image format designed
primarily to be portable
across different platforms.
It is not particularly space efficient, but can be handled by many
different image manipulation programs.
There is also a binary variant
that is more space efficient but less portable.
-
ppt
-
A Microsoft
PowerPoint
document. It is binary
but will work directly on any machine that has Microsoft
PowerPoint or Apple Keynote. Note that neither of these products
is free, so this is not a good distribution
format. Also, Microsoft has split this format into two different variants (one uses the PPTX extension while the other uses the PPTM extension) in newer versions of PowerPoint.
-
pptm
-
This extension is used by one of Microsoft's replacements for the PPT format. It can only be read by machines with MS-PowerPoint (at least version 12) installed. Note that unlike the PPTX variant, these files can contain embedded code (the "m" stands for "macro") and should thus not be considered safe if they come from untrusted sources.
-
pptx
-
This extension is used by one of Microsoft's replacements for the PPT format. It can only be read by machines with MS-PowerPoint (at least version 12) installed. It is a safer sibling to the PPTM format.
-
pqa
-
A Palm query
application is used to relate a group of
Palm Database
files together.
-
press & pre
-
Press files are typically source files for the Newton
Press program and will work on any computer that has
Newton Press (currently available only on
Macs and
WinTel boxes). Newton Press can
save press files as Newton books.
-
prg
-
A program file is a
program usually for a
C64 or C128 computer,
although it could also be for something else. It will probably not
work on a platform
other than the one for which it was designed.
-
ps
-
Postscript files are
capable of holding quite a variety of information ranging
from pictures to text documents to
font definitions. Postscript
files can be directly interpreted by many printers, and
Postscript viewing software comes with many computers and
can be obtained for free for most others. The most
popular free Postscript viewer is called ghostscript and
may be downloaded from many different FTP sites. In
truth, Postscript is actually a full
language, and Postscript
files can perform all manner of things.
-
psd
-
The PhotoShop
Data image
format was developed
by Adobe for use with its PhotoShop
program and can
be read by any machine that has it installed (current versions are only
available for Macs and WinTel boxes, and then not
for free).
-
pxr
-
The
Pixar
image format was
developed by Pixar and can read by numerous different
image manipulation programs
for several different platforms.
-
py
-
Usually a Python script, a
program written in the Python
language. It should run on any machine that has
Python installed and is typically in simple
ASCII.
-
pyc & pyo
-
Usually a compiled
Python
script (that is, Python
bytecode), a
program written in the Python
language. It should
more or less run on any
machine that has Python installed, but unlike
py files will probably be
binary rather than simple
ASCII. In the case of the
"pyo" variant, the script is not only compiled but
optimized.
-
pyd
-
Usually a Python
shared library. It
is binary and not
portable.
-
qxd
-
A Quark XPress
document. It is
binary
but will work directly on any machine that has Quark XPress
(currently only available for
Macs and
WinTel boxes).
-
r00 - r99
-
This file is designed to work on any machine that has C64
emulator
software (C64 emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the C64 (or C128) itself. It is essentially
a repackaging of a regular Commodore
relative file. Note that
relative files are generally quite rare, and some lesser emulators
may not be able to handle them.
-
rar
-
The rar format is used
for archival purposes.
-
ras
-
The Sun rasterfile
format is an old image file
format that is no longer all that common. Many image
processing programs are
capable of reading this format, however, so it can
generally be used on most platforms.
-
rb
-
A Rocket e-book
file. It is
binary and not particularly
portable; in fact it is
geared primarily toward dedicated e-book
hardware.
-
rel
-
A relative file used by
C64 or C128 computers.
Relative files are a complex data storage system directly supported by the
C64/128 operating system. It is quite different from the more common
sequential data file
more typically used by Commodore, and is not supported by any Commodore versions
of GEOS.
-
rle
-
A Utah run length
encoded file image file can be viewed
with free viewer programs on
most platforms, but will not be
directly recognized by most browsers.
-
rm
-
A RealMedia movie file will typically store a
movie clip. It's generally supported by many different platforms.
-
rnq
-
A Renque
file contains data representing a discrete event simulation model that can be read by the application Renque (currently available only for MS-Windows). It is a simple ASCII format.
-
rsrc
-
A
resource
file contains data to be
used by Mac OS
programs and will typically
accompany C or
C++ source files. It is
binary and specific to the Mac.
-
rst
-
This is probably a restructured text document. It is like a structured text document in that it is essentially an ordinary text document that uses careful structuring to indicate format, but it uses slightly different rules making the two a little different in the details.
-
rtf
-
A rich-text
format file
attempts to provide more formatting capabilities than simple
ASCII while maintaining
portability. Unfortunately
different versions of RTF are not always 100% compatible,
so it is not 100% reliable.
-
ruby
-
Usually a Ruby
script, a
program written in the Ruby language. It should
run on any machine that has
Ruby installed and is typically in simple
ASCII.
-
s00 - s99
-
This file is designed to work on any machine that has C64
emulator
software (C64 emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the C64 (or C128) itself. It is essentially
a repackaging of a regular Commodore
sequential file.
-
scpt
-
Usually an AppleScript script, a program written in the AppleScript language. It typically runs only on Macs.
-
sda
-
A self-dissolving
archive contains
compressed data that should in
theory decompress itself when run.
The primary problem is that it will be
platform
specific and will only decompress properly on the same
type of platform that was used to create it. Similar in
principle to a self-extracting
archive but different in practice. Note too that StarOffice (pre
version 6.0) saves its drawing program documents with
this extension; these can be read on any machine with
StarOffice or OpenOffice installed (available for many
platforms including
WinTel boxes,
Macs,
OS/2 boxes, and several types of
UNIX boxes).
-
sdc
-
A StarOffice (pre version 6.0)
spreadsheet document; can
be read on any machine with StarOffice or OpenOffice
installed (available for many
platforms including
WinTel boxes,
Macs,
OS/2 boxes, and several types of
UNIX boxes).
-
sdd
-
A StarOffice (pre version 6.0) presentation program
document; can be read on any machine with StarOffice or
OpenOffice installed (available for many
platforms including
WinTel boxes,
Macs,
OS/2 boxes, and several types of
UNIX boxes).
-
sdw
-
A StarOffice (pre version 6.0)
word processing
document; can be read on any machine with StarOffice or
OpenOffice installed (available for many
platforms including
WinTel boxes,
Macs,
OS/2 boxes, and several types of
UNIX boxes).
-
sea
-
A self-extracting
archive contains
compressed data that should in
theory decompress itself when run.
The primary problem is that it will be
platform
specific and will only decompress properly on the same
type of platform that was used to create it. Similar in
principle to a self-dissolving
archive but different in practice.
-
seb
-
A Franklin e-book
file. It is
binary and not particularly
portable; in fact it is
geared primarily toward dedicated e-book
hardware.
-
seq
-
This is a generic sort of extension indicating a simple sequential
data file. It may be either
ASCII or
binary, and may
contain data from pretty much any
character set.
A file with this extension may or may not be
portable. This
particular extension is used heavily on
C64 or C128 computers,
so there is a high probability that files with it were intended
for such a machine.
-
sfl & sfp
-
The SoftFont
format is used for storing
bitmapped
fonts. It is a product of
Hewlett-Packard and is supported by many HP printers. The
SFL variant indicates the font is to be used in landscape
orientation. The SFP variant indicates portait
orientation.
-
sfs
-
The SoftFont
Scalable format
is used for storing vector
fonts. It is a product of
Hewlett-Packard and is supported by many HP printers.
-
sfx
-
A
self-extracting
archive contains compressed
data that should in theory decompress itself when
run. The primary problem is that it
will be platform
specific and will only decompress properly on the same
type of platform that was used to create it. Similar in
principle to a self-dissolving
archive but different in practice.
-
sh
-
Probably a Bourne Shell script.
It will work on any machine that has the Bourne Shell or Bourne-Again Shell
installed.
-
shar & sha
-
Groups of files are often sharred together so that they
may be handled as a single file. A file that ends with
this extension is probably such a file and will have to
be unsharred into its individual components before use.
The whole concept of sharring started on
UNIX machines, but it is also
possible to get programs to shar and unshar on most other
computers.
-
shtml & shm
-
An HTML file utilizing
server-side includes. An SHTML file can be somewhat dynamic; a
typical use is the automatic inclusion of a "last
modified" date.
-
sid
-
A SID audio file is a program
that will directly run on a computer with a SID chip (like a
C64 or C128 or a
WinTel box with appropriate hardware).
As an audio format, it is fairly efficient. Furthermore, free SID players are available
for most platforms, and there
are even free SID playing plug-ins
available for Netscape and compatible
browsers.
-
sit
-
A file that has been compressed with Aladdin's
Stuffit program will
get the "sit" extension. It is similar in performance to
gzip, but less
portable. Unlike gzip, sit
does not require a separate tarring
step; it uses its own method to do the equivalent.
-
snf
-
The Server Normal
Format is a
format for storing
bitmapped
fonts. It is
machine-dependent; that is, do not expect that a file in this format
from one machine will work on another. Virtually every machine
that uses SNF fonts will be able to convert them to BDF, though.
-
so , dll , & dylib
-
A shared library object
(also called a dynamically
loaded library or dynamic
library). Whatever they are called, these things are
binary
and extremely platform-specific;
they may fail to be usable even on two machines of the same model
and OS based upon other less
obvious specifics.
-
spd
-
The Speedo
format is used for storing
vector
fonts. It originated on the
X-Windows system and is
a creation of the Bitstream, Inc. company.
-
spx
-
The Speex format is
a binary audio
format designed for holding speech. It is patent and royalty free, and
is supported on most platforms.
-
stx
-
This is probably a structured text document. It is like an ordinary text document but utilizes careful structuring to indicate format.
-
svg
-
A Scalable Vector Graphics file contains XML data representing an image. It can be viewed by any application that can understand SVG data.
-
swf
-
A playable Macromedia Flash animation. Playable on any
machine with the free Macromedia Flash player, currently
available for (at least) Macintosh,
MS-Windows, and
UNIX often as a
plug-in available for Netscape
and compatible browsers.
-
sxc & stc
-
A StarOffice (version 6 and later) or OpenOffice
spreadsheet document (they
are the same); can be read on any machine with StarOffice
or OpenOffice installed (available for free for many
platforms including
WinTel boxes,
Macs, and some types of
UNIX boxes). The version with the
"x" is an ordinary document; the version with the "t" is
a template for building other documents.
-
sxd & std
-
A StarOffice (version 6 and later) or OpenOffice drawing
program document (they are the same); can be read on any
machine with StarOffice or OpenOffice installed
(available for free for many
platforms including
WinTel boxes,
Macs, and some types of
UNIX boxes). The version with the
"x" is an ordinary document; the version with the "t" is
a template for building other documents.
-
sxi & sti
-
A StarOffice (version 6 and later) or OpenOffice Impress
document (used for holding presentations -- the two use
the same format); can be read on any machine with
StarOffice or OpenOffice installed (available for for
free for many platforms
including WinTel boxes,
Macs, and some types of
UNIX boxes). The version with the
"x" is an ordinary document; the version with the "t" is
a template for building other documents.
-
sxm & stm
-
A StarOffice (version 6 and later) or OpenOffice math
document (they are the same); can be read on any machine
with StarOffice or OpenOffice installed (available for
free for many platforms
including WinTel boxes,
Macs, and some types of
UNIX boxes). The version with the
"x" is an ordinary document; the version with the "t" is
a template for building other documents.
-
sxw & stw
-
A StarOffice (version 6 and later) or OpenOffice
word processing
document (they are the same); can be read on any machine with
StarOffice or OpenOffice installed (available for for
free for many platforms
including WinTel boxes,
Macs, and some types of
UNIX boxes). The version with the
"x" is an ordinary document; the version with the "t" is
a template for building other documents.
-
t64
-
The C64 tape
file stores the contents of an entire
C64
tape in a single
file. It is
binary, but
is designed to work on any machine that has C64
emulator
software (C64 emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the C64 (or C128) itself.
-
tar
-
Groups of files are often tarred together so that they
may be handled as a single file. A file that ends with
this extension is probably such a file and will have to
be untarred into its individual components before use.
The whole concept of tarring started on
UNIX machines, but
it is also possible to get programs to tar and untar on most other
computers.
-
tcl
-
A file with this extension
is typically a program
written in the Tcl
programming language.
It should be in simple ASCII
and should be usable on any machine with Tcl/Tk.
-
template & tem
-
A template file written in the C++
programming
language. It should be in
simple ASCII and
(depending upon how portably
it was written) should be usable on any machine with a C++
compiler. A template file will
typically also require some C and h files to be used in any meaningful way.
-
tfm
-
The TEX Font
Metric file is used to provide
information on TEX
fonts. It is
binary, but will work
on any machine that has TEX installed.
-
tga
-
The Targa image format can read by numerous
different image manipulation programs
for several different platforms.
It is frequently used in special effects and raytracing work.
-
tgz
-
It is so common to tar a batch of
files and then compress them with gzip
that the result is often given the "tgz" extension
instead of "tar" and "gz" in sequence.
-
thtml & ttml
-
Very similar to shtml but utilizes
Tcl to do its work.
-
tiff & tif
-
The tagged image
file format is a lossless format for
storing image data. TIFF is a popular output format for
scanners and other
similar devices. Free viewers exist for TIFFs on most platforms, but most browsers lack direct TIFF
support.
-
topc
-
This is a simple ASCII
file used by the TopicCrunch program (available only on MS-Windows) to store keywords plus domain and search engine settings to allow re-running search engine optimization checks.
-
tr
-
A TomeRaider e-book
file. It is
binary and not particularly
portable; it can
currently only be used with Palm Pilots,
Psions,
Windows '98, and some flavors of
Windows CE. It is
currently not supported on any other type of
PDA or
OS.
-
tsv
-
This file type is used to exchange data between numerous spreadsheet
and database applications. It is in simple ASCII (in fact, it
is just a collection of tab-separated
values) and is
platform-neutral.
-
ttf
-
The Truetype
Font format
is used for storing vector
fonts. It originated on
Macintoshes and
WinTel boxes and can
be made to work on many other systems as well. Unfortunately there
are two slightly different Truetype formats in use;
modern Macintoshes can use either, WinTel boxes are
restricted to the WinTel type, and other systems can
sometimes use either but will usually be restricted to
one or the other. Free conversion programs exist to
convert between the two.
-
txt & text
-
This is a generic sort of extension indicating a simple
text file (usually ASCII).
It can be readily used on virtually any computer, although sometimes
character set
differences will require slight conversions. A file with this
extension will not typically have significant formatting;
that would decrease its simplicity and portability.
-
type
-
This is a generic sort of extension indicating some sort
of "type" data; of particular note though is that native
Amiga
font files often
use this extension.
-
u00
-
This file is designed to work on any machine that has C64
emulator
software (C64 emulators are available for many platforms, including
UNIX,
Macs, and
WinTel boxes)
as well as (of course) the C64 (or C128) itself. It is essentially
a repackaging of a regular Commodore
user-defined file.
-
ulx
-
A Glulx data file.
Typically it will represent an interactive fiction story
(or interactive tutorial, or similar). It is
binary but will
work on any machine with some flavor of Glulx interpreter, and such
interpreters are available for several different
platforms,
usually for free. It is currently not as
portable as a
Z-machine file, but
it is being actively developed so this will probably change in time.
-
uni
-
This is a generic sort of extension usually indicating a simple Unicode
text file.
It can be readily used on virtually any computer. A file with this
extension will not typically have significant formatting;
that would decrease its simplicity and portability.
-
url
-
This file is an Internet short-cut. It is used to indicate a URL and can usually be opened with a browser.
-
usr
-
A user-defined file used by
C64 or C128
computers for both data storage and some
applications. Since
they are by definition "user-defined", these can vary wildly
in all details. They are heavily used by all Commodore versions of
GEOS.
-
uu & uue
-
The uuencode program will convert a
binary file to
ASCII, typically for purposes of
e-mailing. A file with
this extension has usually been converted in this way and
will need to be uudecoded in
order to be properly used. The whole uuencoding / uudecoding thing
started on UNIX systems,
but today free uuencoders and uudecoders are available for virtually
every computer platform.
Unfortunately it was never really standardized, so sometimes uudecode on one
machine will not properly work on something that was
uuencoded on another.
-
vbm
-
A video bitmap
file; a monochrome
image format originally designed for
the Commodore 128,
but readable by many other machines as well with the appropriate software. It is essentially a binary version of the X-bitmap format.
-
vf
-
The Virtual Font format is used to store
composite font information. It will work on any machine
that has TEX installed.
-
vor
-
This extension can indicate one of two unrelated things. The more
common one is a file pretty much like an
sdw,
sdd,
sdc, or
sda file, but a
template rather than an ordinary document. The less common is a so-called
Vorpal file: a proprietary
format
designed by Epyx for fast loading from slow devices.
-
vsd
-
A Visio document is a binary file used to hold charts and diagrams. It can be read on any machine that has either Visio or OmniGraffle Pro installed.
-
wav
-
The waveform audio file
format was originally
developed on WinTel
boxes but can now be played on many platforms. It is one of the most
popular audio formats found on the
web. It cannot be
played on as many different machines as mono
au files,
though, so for simple voice recording the au format may
be preferable.
-
wdb
-
A DataViz document; can be read on any machine with
DataViz (MS Works) installed (available only for
WinTel boxes and
Macs, but usually not for free).
-
wdgt
-
Unfortunately this extension can mean one of two slightly incompatible things: an Apple Dashboard Widget or an Opera Widget. In each case it'll function a lot like an applet
desktop accessory. In the former case it will work on computers running Mac OS X or KDE. In the latter case it will work on computers running the Opera browser. The Apple Widget will consist of a group of files kept together in an application bundle; the Opera Widget will consist of a group of files zipped together. See also the similar widget extension.
-
widget
-
This is probably a Yahoo! (formerly Konfabulator) Widget. It'll function a lot like an applet
desktop accessory. It usually consists of a group of files zipped together. See also the similar wdgt extension.
-
wk1
-
A Lotus 123-2 document; can be read on any machine with
Lotus 123 installed (available only for
WinTel boxes,
Macs, and some
UNIX boxes, but usually
not for free).
-
wks
-
A Lotus 123-1A document; can be read on any machine with
Lotus 123 installed (available only for
WinTel boxes,
Macs, and some
UNIX boxes, but usually
not for free).
-
wmf
-
A Windows metafile is
like an ordinary CGM
metafile but possibly containing structures that make it specific to
MS-Windows. It is
not really more capable than the ordinary CGM
format, but less
portable and
therefore less desirable.
-
wp , wp4 , wp5 , wp6 , & wpd , wpp
-
A WordPerfect
document. It is
binary but will
work directly on any machine that has WordPerfect.
-
wps
-
A Microsoft Works word processing document. It is
binary and generally requires Microsoft Works to be read, although some versions of Microsoft Word will read some versions of Microsoft Works documents some of the time.
-
wra & wr3
-
A Wraptor file is similar in all respects to an
arc file, but a
different method of compression
was used. Programs to uncompress
this type of file are apparently only found on the
C64/128.
-
x3d
-
An Extensible 3-Dimensional Graphics file contains XML data representing a 3D image. It can be viewed by any application that can understand X3D data.
-
xbm
-
The X
bitmap
format was designed specifically
for small icons. It is in
simple ASCII and only
supports monochrome. It is supported on many
platforms and most
browsers. It is not space
efficient, but because it is always used for small
images, this is usually not a problem. Historically it is
the original World-Wide Web
image format; the others
came along later.
-
xcf
-
The Experimental Computing Facility
format is used by the GIMP to store image files.
-
xls
-
An Excel spreadsheet
document; can be read on any machine with Microsoft Excel (available only for
WinTel boxes and
Macs, but usually not for free). Note that in newer versions of Excel Microsoft has split this format into two variants that use either the XLSX or the XLSM extension.
-
xlsm
-
This extension is used by one of Microsoft's replacements for the XLS format. It can only be read by machines with MS-Excel (at least version 12) installed. Note that unlike the XLSX variant, these files can contain embedded code (the "m" stands for "macro") and should thus not be considered safe if they come from untrusted sources.
-
xlsx
-
This extension is used by one of Microsoft's replacements for the XLS format. It can only be read by machines with MS-Excel (at least version 12) installed. It is a safer sibling to the XLSM format.
-
xml
-
An extensible markup language file contains data in simple ASCII that can be read with particular applications on a case-by-case basis. Much of the data contained within the World-Wide-Web is actually in this format.
-
xo
-
An "activity" bundle for a OLPC project XO laptop. It is typically an application often (but not always) written in Python bundled into in a single zip file along with all its supporting data.
-
xpi
-
An extension package installer used by Mozilla and several related browsers. It will generally perform the install automatically if entered as a URI.
-
xpm
-
The X
pixmap
format was designed
specifically for small icons.
It is in simple ASCII but
supports multiple colors, even a transparent color. It is
supported on many platforms
and most browsers. It is
not space efficient, but because it is always used for small
images, this is usually not a problem.
-
xps
-
XPS stands for XML Paper Specification and is quite similar in intent to PDF. Being newer, it does not yet have the widespread support that PDF enjoys, though.
-
xul
-
An XML user-interface language file contains XML data that can be parsed by applications that understand XUL.
-
xwd
-
An X-Windows
dump is the
X-Windows variant
of the bmp and
pict image
file formats with
similar limitations.
-
Z
-
The UNIX compress program
is used to reduce the size of a single file. If more than
one file is to be compressed,
they must be tarred together
first. By default the compress program will create a file with the "Z"
extension. This file will have to be uncompressed before
use and will not be easily uncompressed on non-UNIX
systems. It is probably better to use
gzip both for reasons
of portability and compactness.
-
z1 , z2 , z3 , z3 , z4 , z5 , z6 , z7 , z8 , & zco
-
A Z-Machine data
file. Typically it will represent an interactive fiction
story (or interactive tutorial, or similar). It is binary but will work on any
machine with some flavor of Z-machine interpreter, and
such interpreters are available for virtually every
machine in existance (often for free). The 1-4 variants
are classic Infocom style; the 5-8 variants are newer.
Types 1, 2, 4, 6, and 7 are extremely uncommon; most
Z-machine data files are types 3, 5, or 8. Type 8 allows
for a much longer, more complex story than the other
types -- if types 3 & 5 are viewed as being similar
to short stories or novellas, type 8 can be viewed as
being as long (or longer) than a full novel. Type 6
provides some graphics support.
-
zblorb & zlb
-
A Blorb file designed to work within a Z-Machine.
-
zcml
-
Zope Configuration Mark-up Language files are XML files used for the configuration of Zope Web sites.
-
zip
-
A file that has been
compressed with either the
zip or pkzip program
will get the "zip" extension. It is similar in
portability and
performance to gzip (with gzip
being perhaps slightly more portable), and similar in performance (but more
portable than) sit. Unlike gzip, zip
does not require a separate tarring
step; it uses its own method to do the equivalent.
-
zpt & pt
-
Used for creating dynamic XML, a page template is itself an XML file built around a handful of namespaces including TAL, TALES, METAL, and I18N. Originally used only with Zope, page templates are now being used with several applications.
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