File Compression

Lossy discards some data. Lossless uses repeated patterns. WinZip, IZArc, and 7-zip are file compression/decompression utilities.

File compression reduces the size of files making them more efficient to store and to transport across the Internet. There are two types of file compression: lossy and lossless.

• With lossy file compression some of the data in a file is discarded. This type of compression is typically used with pictures and music files. For example, in an image file, data elements that record subtle color changes or shading may be eliminated without seriously degrading the image.
• Lossless file compression does not discard any data. This approach looks for repeated patterns in the data and creates a table of the repeated patterns. The repeating patterns in the uncompressed file are replaced in the compressed file with a pointer to the appropriate location in the table.

You may have received compressed files in an email attachment or downloaded them from the Internet. Frequently, these files have a .zip file extension and are called zip files. Before you can use the files, they must be decompressed or unzipped. Some files can be decompressed by simply clicking on them and others require special compression/decompression utilities such as WinZip or PKZip.

One free compression/decompression utility that is growing in popularity is IZArc. To learn more about this utility, click the link below and view the TechTV video.

File compression video