Compression Schemes
Recognizing a Compressed File
While downloading files from the Web, you will undoubtedly
encounter many different types of electronic files formats. The way
you can identify the file type by looking at its extension, typically expressed as a dot followed by 3 to 4 letters (.xxx).
EXAMPLES: Annual_Report.zip or myfile.sit
Why should you care? You need to know know whether a particular compression scheme will work
on your computer, and whether you will need a particular type of application
to decompress, play, or view a file.
Common Compression File Types
The most popular compression schemes are files with extensions such
as .zip, .sit and .tar. These extensions represent popular compression formats for the PC, Macintosh, and Unix. When you receive attached files with these
extensions, they may be single files or groups of files that have been
bundled together into a single archive.
On Windows platforms, the most widely-used archive format is .zip; other formats are .cab, .rar (file format), and .ace. Windows Installer is a high-level archive format for distribution of software.
On Apple Macintosh, .sit and.zip, which are supported natively in Mac OS X (10.3+).
Others
.ace - A
popular upcoming Windows compression format that can potentially compress
files smaller than WinZip. Compressor / Decompressor software available
as shareware.
.bin - binary
format (Macintosh graphics format)
.cab - The Microsoft Windows native archive format, which is also used by many commercial installers such as InstallShield and WISE
.hqx - A
common Macintosh internet-safe compression format. Generally decompressed
with programs like Stuffit Expander by Aladdin Systems. This program
is available for Macintosh.
.exe (PC) / .sea (Mac) Self-Expanding Archives (respectively). These files
generally "expand" themselves when run from the appropriate operating
system. .EXEs can also represent any Windows executable file.
.mme - Indicates
a Multipurpose Internet Mail Extensions (MIME) file. MIME converts
a binary attachment (a program or word processing document or even
an image) to a text format that can be handled by the machines that
send e-mail through the Internet. Used by AOL
.rar - a proprietary achive format, second in popularity to .zip files (multiple platforms)
.sit / sitx - A
common Macintosh compression format. The "x" indicates "self-extracting". Generally decompressed with programs
like Stuffit Expander by Aladdin Systems. This program is also available
for Windows.
.tar - commonly used in Unix systems
.uu - A
common PC internet-safe compression format, uuencode is generally
decompressed with programs like Stuffit Expander by Aladdin Systems.
Stuffit is available for Windows.
.zip - A
common DOS/Windows compression format. Generally decompressed with
programs like WinZip or Aladdin Stuffit.
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Centers for Teaching and Learning, San Mateo Community College District, CA USA Updated 2/28/2010 by Sevastopoulos
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