Data compression is the process of encoding information using fewer bits (or other information-bearing units) than a more obvious representation would use, through use of specific encoding schemes. For example, this article could be encoded with fewer bits if we accept the convention that the word "compression" is encoded as "comp". One popular instance of compression that many computer users are familiar with is the ZIP file format, which, as well as providing compression, acts as an archiver, storing many files in a single output file.
As is the case with any form of communication, compressed data communication only works when both the sender and receiver of the information understand the encoding scheme. For example, this text makes sense only if the receiver understands that it is intended to be interpreted as characters representing the English language. Similarly, compressed data can only be understood if the decoding method is known by the receiver.
Compression is possible because most real-world data have statistical redundancy. For example, the letter 'e' is much more common in English text than the letter 'z', and the probability that the letter 'q' will be followed by the letter 'z' is rather small. Lossless compression algorithms exploit statistical redundancy in such a way as to represented the sender's data more concisely, but nevertheless perfectly.
Further compression is possible if some loss of fidelity is allowable. For example, a person viewing a picture or television video scene might not notice if some of its finest details are removed or not represented perfectly. Similarly, two strings of samples representing an audio recording may sound the same but actually not be exactly the same. Lossy compression algorithms introduce relatively minor differences and represent the picture, video, or audio using fewer bits.
Compression is important because it helps reduce the consumption of expensive resources, such as disk space or connection bandwidth. However, compression requires information processing power, which can also be expensive. The design of data compression schemes therefore involves trade-offs between various factors including compression capability, any amount of introduced distortion, computational resource requirements, and often other considerations as well.
Compression can be at different compression ratios based on the time/compression trade off. Winzip is used more because of a more intutive interface and faster compression, however the compression ratios is less as compared to winrar.
Novice users generally use Winzip whereas vice versa for winrar in general.
"WinRAR has become the standard archiving tool used on the newsgroups. With the ever increasing size of media files, rar files are popping up in newsgroups that once housed small media files."
WinZip does not support the RAR format. On the other hand WinRAR supports the Zip format, as well as just about anything else.
Most people consider WinZip to be over the hill. Check the comments for the latest release of Winzip at FileForum.