The storing of data in a format requiring less space. In communications, data compression is helpful because it enables devices to store or transmit the same amount of data in fewer bits, thus making the transmission of the data faster. Compression falls into two main categories: lossless compression and lossy compression. With lossless compression, the original data can be restored to be an exact replica of the original, whereas with lossy compression, one accepts some quality losses in the compression/decompression steps. Lossy compression is used mainly for audio and video data, for which the loss in data quality is easily overlooked by the human user. Before data is encrypted, it can be compressed using the compression standard gzip and its compression library zlib. Encrypted data can be entirely noncompressed.