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This page describes several file formats that you may
encounter while surfing the World Wide Web (Web).
For a more complete list of file extensions and their
meanings, click on the Office of Information Technology (OIT)
Help Desk document number 2311.
Zip Files (.zip)
A Zip file is a common data compression format that is available for
download. A Zip file can be one file or
a group of files compressed into a single file. Zip
files always have a .zip extension (filename.zip). The
advantages of using a Zip file format are:
-
Easier and faster to download since you only
need one compressed file.
-
Use less hard-disk space.
There are many free programs available for creating or opening a
Zip file.
-
Winzip is available for all versions of
Windows. This program can be downloaded from the Web at
www.winzip.com/index.htm
for a free trial version.
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Pk-Unzip is available for Windows. This program can be
downloaded from www.pkware.com
Zip files may contain viruses so be careful when opening this type of file.
Do not open a
Zip file if you received it as an attachment from an unknown
source. When you download a Zip file, always scan it for
viruses before you open that file.
Executable files (.exe)
Executable files (usually referred to as EXE files) are
files which are in a format the computer can read and execute.
These files can not be read by humans. Almost every installation
program or application on your Windows computer comes with an
EXE file. Like Zip files, an EXE can contain many other
smaller files in a compressed format, files which can be
extracted or installed by double-clicking on the EXE
file. The advantage of using EXE files is that they can
be downloaded and extracted without having to use an
unzipping program like Winzip or Netzip.
Be aware, however, that EXE files can be also used to spread viruses.
Therefore, use caution when opening them. A good practice
is never to open a file with a .EXE extension unless you know
what it is and who sent it to you. If you get a
suspicious-looking file via email (even if it seems to be
from a friend) do not download it until you find out what it
is. If the person who
sent it to you doesn't know anything about it,
delete the email message.
Image File Formats (.jpg, .gif, and .png)
Joint Photographic Experts Group (JPG) and Graphics Interchange Format (GIF)
files are most common image file formats used on
the Web because of their small size. These files have a .jpg
and a .gif file extension. Web browsers
and most imaging programs can open these
file formats.
Portable Network Graphics (PNG) are supported by the Web
however not all browsers support this file format. PNG
format builds on the GIF images but allows
control of the degree of transparency which is known as
opacity.
Portable Document Format (PDF file types)
The Portable Document Format (PDF) developed by Adobe is a
file format designed to be readable on different computer
platforms such as Macintosh, UNIX, and Windows. The
advantages of using a PDF format instead of a plain text
document is that the PDF document can contain complex
graphics and tables. For these reasons, many online manuals and forms found on
the Web are in PDF format. PDF files are opened with Adobe
Acrobat Reader, a program designed to work with your web
browser to allow you to read these documents on the Web.
Adobe Acrobat Reader can be downloaded for free from Adobe's
Web site at www.adobe.com.
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