In computer terminology compression relates to the reduction in size of data so that one can save on space and transmission time. This can be achieved by compressing the entire transmission unit or compressing the data content.
Content compression can be done by removing all extra space characters, using a single repeat character in place of a string of repeat characters and replacing frequently occurring characters with smaller bit strings. This can reduce the file size by almost half.
Compression techniques can be lossy (some information is lost in the compression process) or lossless (all the content can be restored on decompression). A program that uses a formula or algorithm works on the files and determines how to compress or decompress data. If used carefully, compressing can focus on noise (unwanted disturbances in the picture) and eliminate it, thereby improving quality of the graphic while reducing size. This method of sorting out noise and signal while compressing is known as perceptually lossless compression.
Compression reduces the file size and eliminates non essential elements. But this has to be achieved without compromising on the document quality. Some programs embed images at higher resolutions than required. If size is reduced here and compressed, a lot of space can be saved. Another way to save space is use standard fonts because such fonts do not have to be embedded in the file.
Since compression of documents involves change of data bits, care has to be taken that it does not produce degraded data. There are different versions of the same compression standards available commercially. Therefore it is important to understand which works best in a given situation. A good way to do this is to test the fidelity of the original and compressed document using systems like OCR.
By compressing documents one can save time while sending it over the net. It occupies less storage space and backups of important documents can be compressed and stored in the hard disk. It is also possible to compress many files into one easy-to-manage file with a compression command run just once to compress all the documents.