This document contains definitions of file extensions.
- .AU
- AU is a sound file format developed by Sun for the Unix platform for use
on The Internet. It is known as the Sparc-audio or u-law format.
- .AVI
- Audio Video Interleafed
- A sound and video file format developed for the Microsoft Windows platform.
It is based on the Microsoft Windows Resource Interchange File Format (RIFF)
specification. A special player is required to play these files.
- .DTD
- SGML (and XML) Document Type Definition file
- .fif
- Fractal Image Format
- FIF is a bitmap compression format for storing graphic file data. Fractals
are geometrically describable units originally developed by Benoit Mandelbrot
in the 1960s that reflect the patterns of nature much better than traditional
Euclidean geometry.
- .fla
- A Flash file extension
- The .fla file extension is used for the basic Flash document
file, used in the development context. After its development, a Flash document
needs to be "published" to the Web. It then gets a .swf
extension which can be played with a Flash player.
- GIF
- Graphic Interchange Format
- GIF is a bitmap method of compressing images,
originally developed for quicker transport of images on The Internet, as
file sizes of other graphic formats were too large. GIF87 is the basic compression
scheme, while the later GIF89a supports transparency and animation.
- Layering: GIF images that have more than 256 colors can be layered in
order to display the image properly. Your graphics program must have the
ability to save the file as such. Not all browsers support this feature.
GIF uses the LZW (Lempel-Ziv-Welch) lossless compression scheme and supports
8-bit color (ie 256 colors).
- GIFs are typically used for relatively simple images, such as company
logos, stick figures, simple buttons, line images and so on. These images
also have relatively few color hues. For more complex images, rather use
JPEGs.
- .html
- or .htm (used for DOS-based computers who could not understand extension
with more than 3 characters). HyperText Markup Language file format -- the
basic format of the web documents. HTML documents contain pointers to content
in other media, such as images, audio, animation, video or scripts. None
of these other media is "inside" an HTML document.
- .JPEG / .JPG
- Joint Photographic Experts Group
- Pronounced jay-peg.
- JPEG is a bitmap compression format for images.
The proper abbreviation is JPEG, but DOS-based computers could only take
a 3-character extension, so you will often see the shortened version: JPG.
JPEG is based on a 24-bit color palette, but it is lossy, which means that
it drops information that is compressed out. Compression ratios may range
from 10:1 to 20:1 and most graphic application programs (such as Adobe Photoshop)
allow you to choose the compression rate. Obviously, the more compressed,
the more data is lost, but the less compressed the larger the files size
of the image. It takes considerable experience and skill to play around
with different modes and pallettes as well as compression ratios to get
a good quality result with a relatively small JPEG file size. JPEG is typically
used for complex images and photographs. It supports 16.7 million colors.
- .MIDI
- Musical Instrument Digital Interface
- MIDI is a system containing music related commands for a synthesizer or
other MIDI-compliant device. A MIDI file thus does not contain any music,
but instructions about music events and objects. The device interprets the
commands in the MIDI file and reproduces the music-related events. A MIDI
file can only be rendered as playable sound on a PC if there is an onboard
synthesizer -- or at least a MIDI connected synthesizer to the PC. MIDI
files can be embedded in HTML files. MIDI files take the extension *.MID
or *.MIDI.
- .mov
- This is the Apple QuickTime format for digital video files.
- .MP3
- MP3 is a sound compression format based on MPEG-1, Layer 3, which is the
audio compression format used in the MPEG-1 algorithm.
- .ogg
- .ogg is the file extension for Ogg Vorbis files. This is an open source
patent-free audio compression format that can be used instead of proprietary
digital audio encoding formats, such as MP3.
- .PNG
- Portable Network Graphics
- PNG is a bitmap compression method for image
files. This format is recommended by the W3C to be used instead of GIF.
PNG supports 16.7 million colors, it is lossless and also supports index
color, grayscale, true color, and is streamable. It is thus the best compression
method (better than GIF or JPEG) for use on the web.
- SGML
- Standard Generalized Markup Language
- ISO 8879 of 1986.
- SGML is an international standard for the transport of documents in a
format independent of the device, system or application.
- The technical detail need not bother you as HTML author. But note that
this standard is also constantly in the process of being revised. In 1993,
for example, Korean Hangul characters have been added to the standard. Also,
there is presently a restriction on the total of codepoints allowed in the
document character set. This is also in the process of being revised.
- SGML is the granddaddy of HTML and XML.
HTML is an application of SGML, while XML is a metalanguage based on SGML,
used for creating XML applications.
- .swf
- A Flash file extension
- The .swf file extension is used for a Flash document that can
be played with a Flash player. Before it is published, a Flash document,
while it is being developed, has the extension .fla.
- SVG
- Scalable Vector Graphics
- W3C Proposed Recommendation 19 July, 2001
- SVG is an XML-based application based on the
vector graphics model. SVG images can
be written with a text-editor, but to do that you need to know vector graphics
inside-out. In 2001 you need a plug-in for your browser to be able to display
SVG files. In future releases of browsers they will most probably support
SVG from scratch.
- TIFF
- Tagged Image File Format
- TIFF is an image file format system used in graphic programs. TIFF is
a compressed bitmap format.
- VRML
- Virtual Reality Modeling Language
- VRML is a modeling language for creating 3-D virtual worlds. VRML is much
more complex than HTML and requires programming knowledge, although some
application tools make it easier to create virtual worlds. VRML files are
quite large and you have to wait for them to load before you can travel
through the world. Older browsers require plug-ins to render the worlds.
- .WAV
- A wave file (*.WAV) is a compressed waveform file used for transporting
sound files through The Internet. Waveform is a Microsoft Windows format,
but such a file can be played back on other platforms (Such as Macs) with
the necessary player software.
- XML
- Extensible Markup Language
- W3C Recommendation 10 February 1998
- XML is a subset of SGML and is a metalanaguage providing the rules and
conventions to be used to create other languages following these rules.
These other languages are called XML-applications. There are thousands of
XML-applications such as MathML (Mathematics Markup Language), CML (Chemical
Markup Language), CDF, OSD, HDML (Handheld Device Markup Language), RDF
(Resource Description Framework), MML (Music Markup Language) - see Robin
Cover's XML pages for a complete list (http://www.oasis-open.org/cover/sgml-xml.html).
- XML documents can be created with a text-editor just like HTML documents.
XML, however, is much stricter with its rules. XML documents need to be
well-formed (e.g. element names, i.e. tags, are case sensitive and must
be ended, unlike HTML) and for data vailidity they also need to be valid
(i.e. be associated with a DTD which contains definitions
of and relationships between elements).
- XSL
- Extensible Stylesheet Language
- W3C Working Draft 21 Apr 1999
- XSL is a style sheet language based on the principals of XML
and more powerful than CSS. XSL consists of two main components: XSLT
(which concerns the document tree) and formatting (which is based on CSS
2.0).