In the process of 5B/6B encoding, it is possible to have the following two kinds of data sequences: 1. 25=32 data sequences 2. 26=64 data sequences Therefore, this can left us with some unused code sequences that are 32 in number (=26 – 25). On the other hand, in the encoding process of 3B/4B, it is possible to another set of data sequences as follows: 1. 23=8 data sequences 2. 24=16 data sequences This type of encoding also leaves us with some unused code sequences that are 8 in number (=23-24). 2.