While surfing the Internet, you will no doubt find text, graphics, audio
and video files to download. Multimedia files can be very large, which
means they move very slowly across the global network. Downloading these
files may take hours, depending on the speed of your Internet connection.
To make efficient
use of disk space and speed things up, most large files are compressed.
File compression reduces the size of a file, reducing the time it takes
to download.
Compression software
uses complex mathematical equations to scan a file for repeating patterns
in the data. It replaces the data with smaller codes that take up less
room. For example, one way compression software works is to replace
repeating text characters with a code that also notes the locations
of those characters in the data. With a picture, it would find all of
the red pieces, for example, and replace them with a code.
To view compressed
files, you need a compatible decompression program that can read these
codes and convert the data back to its original form.
Most of the files
you encounter on the Web are either text, graphics, audio, or video
files. Some may be compressed, others not. The most common compressed
files are those with extensions such as .zip, .sit and .tar. These extensions
represent popular compression formats for the PC, Macintosh, and UNIX.
They may be single files or groups of files that have been bundled together
into a single archive. An archive file can sometimes contain video or
graphics files within it and often contains software programs with related
documentation.
To decompress a
.zip file you need an utility like WinZIP or PKUNZIP, which are available
on the Internet. To unstuff a file with a .sit extension, you need a
program called Stuffit Expander, a popular program for the Mac. Though
PKZIP will not decompress files that have been "stuffed,"
there is a StuffIt Expander version for Windows. StuffIt Expander can
also decompress other formats, including .zip
Files with a .sea
or .exe extension are self-extracting files for the Macintosh and Windows.
They don't require additional software to run. You simply click on the
file to launch it.
TIP: Create a Download
folder on your hard drive, download the compressed file into this empty
folder and decompress it into the folder. This allows you to keep track
of the files that come out of the compressed file. You never know how
many files might be contained in a compressed file.
For more information
about compression, read the Compression FAQ [Frequently Asked Questions]
that is available online at http://www.faqs.org/faqs/compression-faq/.
To download decompression
software, visit http://www.Shareware.com.
Download
Files: File Formats and Extensions
While downloading files from the Web, you will undoubtedly encounter
many different types of electronic files formats. The way to identify
the file type is by looking at its extension, usually expressed as a
dot followed by 2 to 4 letters (.xxx).
Why should you care?
You need to identify the file type to know whether it will work on your
computer, and whether you will need a particular type of software to
view, play, or decompress it.
Many sites make
files available for both Windows and Macintosh operating systems. Your
browser has the ability to identify and display some, but not all of
them, and new ones appear all the time. You probably only need to know
about the most common Internet file formats, so below you will find
some information about them.
Most of the files
will be either text, graphic, audio or video files. Some may be compressed,
others not. The most common compressed files are those with extensions
like .ZIP, .SIT and .TAR. These extensions represent
popular compression formats for the PC, Macintosh, and UNIX. They may
be single files or groups of files that have been bundled together into
a single archive.
An archive file
can contain video or graphics files, and often contains software programs
with related documentation. Occasionally you may come across files with
multiple extensions like .tar.gz, which usually means more than one
type of software was used to compile and compress the file.
The most common
graphics file formats on the Web are those with the extensions .jpg
and .gif.
The .jpg
is short for JPEG, which is a popular compression standard for
photographs and other images. The .gif extension stands for Graphics
Interchange Format, a standard developed by CompuServe in the late
1980s.
Both these graphics
formats are "platform-independent", which means you can use
them on a PC, Mac or UNIX machine as long as you have a viewer for them.
For video, popular
extensions are .AVI and .RAM for the PC, .MPG (short for MPEG), which
is platform-independent, but requires its own player, and .MOV and .QT
for QuickTime movies. QuickTime was initially developed just for the
Macintosh, but now play on Windows and UNIX, too.
The most popular
sound file format these days is .MP3 for both Mac and PCs. Other file
formats include .AIFF (for Mac); .AU for Mac and UNIX; .WAV for the
PC; and .RA for Real Audio, a proprietary system for delivering and
playing streaming audio on the Web.
All of the file
formats found on the Internet can be broken into one of two types: ASCII
format and binary format. ASCII files are text files you can view with
a DOS Editor or any word processor. Binary files contain non-ASCII characters.
If you display a binary file on your screen, you will see a lot of strange
symbols and characters.
The following is
a guide to common Internet file formats.
Plain
Text (ASCII) Files
.html / .htm The
language in which Web documents are authored. File Type: ASCII This
file type requires a web browser, such as Navigator or Internet Explorer,
for viewing.
.txt
A plain (ASCII) text file. File Type: ASCII These files can be viewed
with a word processor like Microsoft Word or a simple text editor like
Simple Text or BBEdit for the Mac. For the PC you can use Notepad that
comes with the Windows operating system.
Formatted Documents
.doc
A common PC format for formatted text files. File Type: ASCII
Although you may occasionally come across files with this extension
that are not text documents, usually they are documents that were created
using Microsoft Word or WordPerfect for Windows.
.pdf
Portable Document Format, a proprietary format developed by Adobe Systems,
Inc. that allows formatted documents (including brochures or other documents
containing artwork) to be transferred over the Internet so they look
the same on any computer. File Type: Binary
This file type requires the Adobe Acrobat Reader to view files and can
be downloaded from the Adobe website.
.ps
A PostScript file. File Type: ASCII Though it is technically a plain
text file, it is essentially unreadable except by a Postscript printer
or with the help of an on screen viewer like Ghostscript, which is available
for Mac, Windows, and UNIX.
Compressed and Encoded Files
.arc
An old and inefficient format for archiving and compression. File Type:
Binary
If you need to exchange files with an older operating system or have
old files to read on a new machine, you may need an ARC program. Stuffit
Expander for Windows will work for the PC (sitexxx.exe). For the Mac
try something called ARCMac.
.arj
A somewhat common format for MS-DOS machines, especially in Europe.
File Type: Binary
It is fairly slow and in some cases may do a better job than the more
common gzip, zip and Stuffit formats. You can use Stuffit Expander for
Windows or WinZIP. On the Mac, try UnArjMac.
.bin
A Mac binary II Encoded File. File Type: Binary
This file type requires Stuffit Expander for the Mac. You download this
type of file as MacBinary or Binary.
.exe
A DOS or Windows program or a self-extracting file. File Type: Binary
If this is an executable (self-extracting) file, then it can usually
be launched by double-clicking on the icon on your desktop. This is
the only way to tell if it is an executable file.
.gz / gzip
The GNU Project's compression program, most commonly used for UNIX and
PC files. File Type: Binary
For the Mac, use MacGZIP. There are several Windows-based GZIP uncompressors
available.
.hqx
A common Macintosh encoding format. File Type: Binary
A file with the .hqx extension is a Macintosh binary file that has been
converted into ASCII text so it can be safely sent over the Internet.
You can use Stuffit Expander to decode on the Mac or BinHex4 (binhex4.bin)
to create and extract Binhex 4 files. Use BinHex13 (binhex13.zip) on
a Windows machine to un-binhex it.
.sit
A Macintosh file that has been compressed using a program called Stuffit.
File Type: Binary
To unstuff a file with a .SIT extension, you need a program called Stuffit
Deluxe or you can use Stuffit Expander for the Mac or for Windows. All
three versions can decompress other file formats as well.
.sea
A Macintosh self-extracting archive file. File Type: Binary
An archive file is usually a collection of files that have been combined
into one to make it easy to download. Because the archive is self-extracting,
you don't need any special application or utility to launch it. You
simply click on the icon from the Macintosh desktop and it decompresses
and unbundles the files.
.tar/.tar.gz/.tar.Z/.tgz
A UNIX archiving scheme that is also available for PCs. File Type: Binary
Tar, which is short for Tape ARchive, can archive files but not compress
them, so .tar files are often gzipped, which is why you might occasionally
encounter the file extension .tar.gz. To download and use .tar files
on a Mac, you use a program called Tar. For Windows you can use WinZIP
to view and extract archive files.
.uu
A UUencoded file. File Type: Binary
UUencoding allows the user to convert binary data into text so it can
be sent via e-mail. You don't often see the .uu extension because many
e-mail programs automatically decode it in a way that is invisible to
you. If your mail program doesn't UUdecode files, then you can use UU
Undo for the Mac and WinCode to UUdecode in Windows.
.Z
A UNIX compression format. File Type: Binary
You can use WinZIP to decompress and view files with this extension,
or try Stuffit Expander for the Mac. You can also use gzip to decompress,
but not create, these file types.
.zip
A common compression standard for DOS and Windows that uses a DOS utility
called PKZIP. File Type: Binary
These files can be decompressed on the PC with WinZIP. You can get copies
for Windows 3.1 and Windows 95/98/2000 (winzipXX.exe). You can also
use Stuffit Expander for Mac or Windows.
Graphics
Files
.gif
The most common graphics file format on the Internet, it stands for
Graphics Interchange Format. File Type: Binary
If your browser does not have a built-in GIF viewer (but most do), then
you can use Lview Pro (lviewpxx.zip) or PolyView (polyvxxx.zip) to view
these graphics on a Windows PC. On the Mac, a shareware utility called
GIF Converter can be used to view and modify GIFs.
.jpg/jpeg/jfif
A popular compression standard used for photos and still images. File
Type: Binary
JPEG files can be viewed on any platform as long as you have a JPEG
viewer. You can view JPEG files with most web browsers. For the Mac,
use JPEGView; for the PC, you can use Lview Pro or PolyView.
.tiff
A very large, high-resolution image format. File Type: Binary
Use JPEGView for the Mac and Lview Pro or PolyView for the PC.
All of the above
graphics formats can be readily viewed, created, or manipulated with
one or more commercially available graphics software programs like PhotoShop
or DeBabelizer for the Mac, and Photostyler or PhotoShop for Windows.
Sound Files
.au/uLaw/MuLaw
The most common sound format found on the Web. File Type: Binary
Macs need Sound App to play this type of file; PCs can use Waveform
Hold and Modify (whamxxx.zip) which provides support for a variety of
formats, conversion between them, and file editing functions.
.aiff
Another fairly common sound format found on the Web. File Type: Binary
Although it is a Macintosh format, it can be used on other platforms
as well. It requires the same programs as .au to play.
.mp3
The most popular file format on the Web for distributing CD-quality
music. A 1 Mb files is equal to about one minute of music. File Type:
Binary
This type of file requires an MP3 player, which is available for both
Macintosh and Windows.
.ra
A proprietary streaming audio format called RealAudio. File Type: Binary
Developed by RealNetworks, RealAudio allows you to play sound files
in real-time. This type of file requires the RealPlayer, available for
both Macintosh and Windows.
.wav
The native sound format for Windows. File Type: Binary
On the Mac, you can use Sound App to play .wav files. For the PC, use
aveform Hold and Modify or Goldwave to play these files. There's also
a good program called Win Play! (wplnyxx.zip) that will play it, as
well as other popular formats.
Video Files
.avi
The standard video format for Windows. File Type: Binary
These files need an AVI Video for Windows player (aviprox.exe) or the
Windows Media Player from Microsoft.
.mov/.movie
The common format for QuickTime movies, the Macintosh native movie platform.
File Type: Binary
You can use a number of applications to play .mov files including Sparkle
or MoviePlayer on the Mac, and QuickTime for Windows.
.mpg/mpeg
A standard format for "movies" on the Internet, using the
MPEG compression scheme. File Type: Binary
On the Mac, use Sparkle to play ,mpg files or to convert them to QuickTime
movies. There are a variety of MPEG Players for Windows and an MPEG
FTP Site that has a large collection of MPEG player resources for all
platforms (Mac, Windows, and UNIX).
.qt
Another extension that denotes a QuickTime movie. File Type: Binary
Use the latest version of Quicktime for the Mac.
.ram
A popular format from RealNetworks for streaming video. File Type: Binary
To view these files, you need the RealPlayer, which can be downloaded
from http://www.Real.com
NOTE:
To download software to decompress, view, or play any of the file formats
covered here, visit http://www.Download.com
Downloading
Software: Step-by-Step
Follow these steps
for downloading applications, plug-ins, games or any other software
from the Internet.
If you don't already
have one, create a Temporary Files folder by opening Windows Explorer,
highlighting your hard drive usually the c: drive), then selecting File/New/Folder.
When the folder
appears, name it Temporary Files.
Once you locate the software you want to download, click on the link
to begin the download process.
You will be asked
where to save the file.
Locate the Temporary
Files folder on your hard drive and double click on it to open it.
Click SAVE
If you are really
bored, you can watch the file as it downloads.
After the download
is finished, you have to install the software.
Close all programs
that are running, except Windows Explorer.
Find the file you
downloaded and double click on it.
A series of installation
screens direct you through the process.
New application
programs are usually installed in the Program files folder. Plug-ins
are usually installed in the appropriate browser folder.
After the software is installed you can delete the file in your Temporary
Files folder to free up space on your hard drive.
