V.42bis Data Compression Software

GAO’s V.42bis software for data compression enhances the performance of error correcting modems by making better use of an often over-crowded communications channel. By using a variable length code to represent fixed length characters, the most commonly transmitted characters are compressed and represented by a codeword much smaller than the conventional bit code. GAO V.42bis encodes a string of characters with a fixed length code. The system uses a dictionary, which has a hierarchical tree structure, to store frequently occurring character strings, along with a code to represent these character strings.