V.42bis and other Ziv-Lempel variants

Summary form only given, substantially as follows. The V.42bis standard for data compressing modems is discussed from algorithmic, experimental, practical, theoretical, and marketing standpoints. On a test set of five 100-Kbyte text and executable files, the compression ratios are found to be markedly inferior to those of several other algorithms, notably the Cleary-Witten adaptive Markov code and the Fiala-Greene Ziv-Lempel variant. However, since all the better-compressing methods have much larger data structures none is superior to V.42bis for use in a contemporary modem