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Lesson 6 Understanding file compression
ObjectiveDescribe Common Formats used for Compressing Files.

What exactly are compressed files?

The word compression means to squeeze together in order to reduce size.
Sometimes files are too large and need to be reduced into a smaller file. Without compressing large files, it would take you a long time to download them. Large files are compressed in platform-specific formats.

Decompressing files

To open compressed files you need decompressing software. Since larger files are prone to increased data transmission errors, some compression software provides error-checking features. Compressed files, also called archive files, carry unique file extensions.


BinHex is an encoding format common for Macintosh files that converts binary data into ASCII for sending over Internet email.
Most email clients use BinHex to send and receive attachments. BinHex formatted files have a .hqx extension.


Gnu's Not UNIX Zip (Gzip) is a data compression utility adopted by the GNU project to run on UNIX and Linux. The format has a .gz extension.


Macintosh Self-Extracting Archive (SEA)compresses multiple files that have been converted into a single executable program. Double-clicking the file causes decompression to occur. Files have a .sea extension.


StuffIt (SIT) by Aladdin Systems, Inc. is a shareware file compression program that compresses files onto multiple floppies. It is a common standard on Macintosh, and files have a .sit extension.


Tape Archive (Tar) is used to archive multiple files into a single file. Tar command does not compress files but generally uses Gzip to compress files. A typical extension would be .tar.gz. The format is supported on UNIX, Windows/NT, and Macintosh platforms.


Zip is a popular data compression format. Zip files are compressed with PKZIP and have a .zip extension. The format is used to zip and unzip files and is supported on Windows/NT and Macintosh.
In the next lesson, you'll learn the purpose of plug-ins.

Compression File Formats

Click the link below to test your understanding of audio/video file formats and formats for compressing files.
Compression File Formats