M OF N CODES

An '''m'' of ''n'' code' is a separable error detection code with a code word length of ''n'' bits, where each code word contains exactly ''m'' instances of a "one." A single bit error will cause the code word to have either ''m'' + 1 or ''m'' – 1 "ones." An example ''m''-of-''n'' code is the 2 of 5 code used by the U.S. Post Office.
The simplest implementation is to append a string of ones to the original data until it contains ''m'' ones, then append zeros to create a code of length ''n''.
Example:

3 of 6 code

Original 3 data bits	Appended bits
000	111
001	110
010	110
011	100
100	110
101	100
110	100
111	000