CHAPTER
12
Commonly Found Internet
File Types
When you use an Internet
search engine to find
something, the information is
almost always returned in the
form of a file. The way in
which the file is organized is
known as its format.
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C H A P T E R 12
Objectives:
 Recognize the commonly found Internet file


types.
Understand how browsers launch different
plug-ins and helper applications to play
certain types of files.
Explain why MIDI files occupy so much less
file space than waveform audio files
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C H A P T E R 12
Objectives:
 Understand the concept of a markup


language.
Know the difference between the GIF and
JPEG graphics formats.
Understand why the audio/video interleave
(AVI) file format was designed to give audio
the priority when a computer does not have
enough processing time to show all of the
frames of a movie.
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C H A P T E R 12
Objectives:
 Explain the difference between lossy and




lossless compression methods.
Understand how animated GIFs can bring a
Web page to life.
Explain the concept of JavaScript.
Understand the purpose of Adobe’s Portable
Document Format.
Avoid the common pitfall of changing a
filename extension when you rename a file.
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C H A P T E R 12
Text Formats
 Plain text means just that—the text and

nothing but the text.
There are three families of text formats:
 Plain text (TXT)
 HTML (Hypertext)
 Word processor files
DOC (Microsoft Word)
WPD (WordPerfect)
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C H A P T E R 12
HTML
How
editor.
HowaaHTML
HTMLfile
fileappears
appearswhen
whenviewed
viewedwith
withaatext
browser.
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C H A P T E R 12
Image Formats
 The computer industry has produced so many

graphics formats (more than 30 at last count)
that there is no true standard across the
industry.
On the Web, however, there are only two file
formats that every Web browser can be
guaranteed to support: GIF and JPEG.
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C H A P T E R 12
Image Formats
 .bmp Windows bitmap. The .bmp file is
the most efficient format to use with
Windows.
 .gif
Graphics Interchange Format.
Invented by CompuServe for use on
computer networks, GIF is the most
prevalent graphics format for images on the
World Wide Web.
 .pcd Kodak’s Photo CD graphics file
format; contains five different sizes of each
picture, from “wallet” size to “poster” size.
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C H A P T E R 12
Image Formats
 .jpg or .jpeg
JPEG image, named for
the standards committee that formed it:
Joint Photographic Experts Group. Intended
to become a platform-independent graphics
format.
 .pict Macintosh graphics format.
 .png Portable Network Graphics format.
Pronounced ping, .png is the patent and
license-free format approved by the W3C
(World Wide Web Consortium) to replace
the patented GIF format.
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C H A P T E R 12
Image Formats
 .tga Truevision Targa format; tga stands
for Targa, which is a video capture board.
 .tif
TIFF file; stands for Tagged Image
File Format. Known as “the variable
standard” because there are so many kinds
of TIFF subformats.
 .wpg WordPerfect graphics format.
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C H A P T E R 12
Waveform Audio Formats
 Every sound has a waveform that describes

its frequency, amplitude, and harmonic
content.
Waveform audio digitizers capture sound by
sampling this waveform thousands of times
per second; the samples are stored in a
computer file.
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C H A P T E R 12
Waveform Audio Formats
 WAV - On multimedia PCs, the most
common waveform audio filename
extension is .wav, which stands for
waveform.
 AU and SND - The Sun audio format
filename extension is .au, and the NeXT
format is .snd. These formats are
essentially the same, except that .au files
do not have file headers to specify different
sampling rates and compression formats.
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C H A P T E R 12
Waveform Audio Formats
 RA and RAM - Real-time audio streaming
used in Internet radio broadcasts requires a
special file format optimized for real-time
transmission over the Internet. The
RealAudio filename extensions are .ra and
.ram, which stands for RealAudio metafile.
 AIF, AIFF, AIFC - AIFF stands for Audio
Interchange File Format. Apple invented this
file format to create and play audio files on
the Macintosh.
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C H A P T E R 12
Waveform Audio Formats
 MIDI Synthesizer Format (MID) - MIDI
stands for Musical Instrument Digital
Interface. MIDI is a music synthesizer file
format that requires very little bandwidth to
transmit, because the sound chip inside
your multimedia PC does the work of
generating the waveform you hear.
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C H A P T E R 12
Waveform Audio Formats
 MP3 - MP3 is one of the most popular
audio formats on the Internet. MP3 stands
for MPEG audio layer 3. It’s an audio file
format that uses an MPEG audio codec to
encode (compress) and decode
(decompress) recorded music. MP3 can
compress a CD-audio track into a
substantially smaller-sized file requiring
significantly less bandwidth.
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C H A P T E R 12
MIDI Synthesizer Format
 MIDI stands for Musical Instrument Digital
Interface. MIDI is a music synthesizer file
format that requires very little bandwidth to
transmit, because the sound chip inside
your multimedia PC does the work of
generating the waveform you hear.
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C H A P T E R 12
Video Formats
 When a movie gets digitized into a computer
file, the digital data stream is enormous. To
conserve filespace and thereby reduce the
bandwidth required to transmit the movie, the
video gets compressed.
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C H A P T E R 12
Video Formats
 Video Compression Schemes
 YUV subsampling - Divides the screen into little
squares and averages color values of the pixels in
each square.
 Delta frame encoding - Shrinks data by storing
only the information that changes between frames;
for example, if the background scene does not
change, there is no need to store the scene again.
 Run length encoding - Detects a “run” of
identical pixels and encodes how many occur
instead of recording each individual pixel.
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C H A P T E R 12
Video Formats
 AVI - The most common video format in
the Windows world is Microsoft’s AVI, which
has the .avi filename extension. AVI stands
for audio/video interleave, which describes
a clever scheme in which audio frames are
interleaved with the video.
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C H A P T E R 12
Video Formats
 MOV and QT - Because of its cross-
platform capabilities, QuickTime has
become very popular on the Internet. The
filename extensions of QuickTime movies
are .qt and .mov.
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C H A P T E R 12
Video Formats
 MPG, MPEG, and MPE - MPEG is
emerging as the digital video standard for
the United States and most of the world.
MPEG stands for Motion Picture Experts
Group, the name of the International
Standards Organization committee that
created it.
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C H A P T E R 12
Video Formats
 RM - RealVideo follows the real-time
streaming protocol (RTSP) that
RealNetworks invented for streaming audio
and video over the Internet, the filename
extension is .rm.
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C H A P T E R 12
Animation Formats
 Animation is the use of a computer to create
movement on the screen. There are several
ways to bring Web pages to life through
animation.
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C H A P T E R 12
Animation Formats
 Animated GIFs - Animated GIFs are a
special kind of GIF file (known as GIF89a)
that may contain multiple images that get
shown in a sequence at specific times and
locations on the screen. A looping option
causes your Web browser to keep showing
the frames in the GIF file continually, and
as a result, you see an animation on
screen.
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C H A P T E R 12
Animation Formats
 JavaScript - As noted earlier, Java is a
programming environment used to create
little applications known as applets that can
be downloaded along with a Web page.
One of the main uses of applets is to make
Web pages become animated.
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C H A P T E R 12
Animation Formats
 QuickTime - Apple Computer Corporation
has created a plug-in whereby QuickTime
movies can be embedded as animation
objects on Web pages. Both Netscape
Communicator and Microsoft Internet
Explorer support this plug-in.
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C H A P T E R 12
Animation Formats
 Shockwave - Macromedia’s Director is the
undisputed leader in multimedia animation.
Shockwave is a Macromedia product that
enables animations created with Director,
Authorware, and Flash to plug in to Web
pages.
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C H A P T E R 12
Portable
Document Format (PDF)
 PDF - To provide a way to digitize printed
text into a format that can be viewed on
any computer platform, Adobe created the
Portable Document Format, for which the
filename extension is .pdf. PDF files are
created by scanning printed documents into
bitmaps that work like photographs of the
printed pages.
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C H A P T E R 12
Avoiding the Pitfall of Renaming
Filename Extensions
 When you save a file you can change the
name of the file. Be careful, however, not to
rename the filename extension.
 Remember that your computer looks at the
filename extension to determine what
application will be used to handle the file.
Renaming the filename extension will only
confuse your computer when you try to
access the file.
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