A step-by-step intuitive explanation for building a DFA to accept ternary numbers that are multiples of 5. A general formula is derived and using that, the transition table of the DFA is computed.

This article explores the problem of accepting strings in ternary format that are a multiple of 3 but not a multiple of 9. Listing out the ternary numbers brings out a pattern for such strings which is expressed as a regular expression and an NFA.

This article explores the differences between the empty string and the empty set. This is followed by few examples of regular operations on these concepts.

Analyzing the formal definition of a deterministic finite automaton (DFA) more closely can result in some uncommon machines. This article explores some extreme cases and the resulting DFAs.