Beginning in the 1970s, computer scientists used mathematical algorithms to search through computer code to find ways to reduce the file size. Since then, there has been an ever-growing need, spurred on by the development of the Internet, to create better compression schemes and reduce the size of any given file as much as possible.
Types of Compression
There are two main types of file compression, lossless and lossy. Lossless compression algorithms search for long strings of code and have a method to replace them with shorter strings. Lossless compression can recreate the entire file exactly as it was. Lossy compression algorithms search through the code to find pieces that it can delete. While lossy compression can't be used on program files, it can be used on multimedia files, where there is often information in the files that human senses cannot detect. When lossy compression is used, the file may appear to be identical, but it is very different at the code level.
File compression reduces the amount of space needed to store data. Using compressed files can free up valuable space on a hard drive, or a web server. Some files, like word files, can be compressed to 90 percent of their original size. Other files, like JPEG or MP3 files, cannot be compressed further since these types of files are already compressed.
The amount of time it takes to send something over the Internet depends on the size of the transmitted file. Compressing files before sending them over the Internet can reduce the amount of time it takes by a considerable margin. It would take one-tenth the time to transmit a compressed word file as it would to transmit that same uncompressed file. File compression also reduces the financial cost of running a network, since less equipment and bandwidth is needed to transmit the data.
Archiving and Backup
When large groups of similar files are stored, such as a group of sequential videos, they can be combined into archive files. Archive files don't have to be compressed, but they are often several gigabytes in size, so they are usually compressed to save storage space and transmission time. Most compression programs also have the ability to archive files into one large file. Most operating systems will compress their backup files, which are very large archive files, since these files just take up space until the need for them arises.
Digital television owes its adoption to file compression technology. The digital television signal takes up much less bandwidth than an analog signal because the digital files are compressed before they are transmitted. In addition to normal file compression, this video compression only transmits the portions of the next frame that changes, which can drastically reduce the file size.