Every program refers to a certain number of states, which are numbered consecutively starting with zero. Very few programs have more than ten states, so the decimal digits can be reserved; typing one inserts the state and advances the cursor. States inappropriate to a given automaton are simply ignored.
- 0,1,2,3, ... - enter state
Between ten and sixteen states, hexadecimal digits can be used, whose letters usurp any other use of the same symbol.
Harold V. McIntosh