A Fuller version of FSAs

• You can do FSAs with equations, but I like diagrams especially for simple ones. It's a directed labelled graph with nodes being states, and arcs marking transitions.
• There is typically an unmarked failure state.
• If an arc is ommitted, it is assumed to go to the failure state, which you can't get out of.
• (In the transition diagram from Buckland, it is assumed that you remain in the same state.)
• You can also have non-deterministic FSAs with null transitions, and multiple arcs for a given label. These are formally equivalent. That is an NDFSA can be automatically converted to a DFSA.
• FSAs are used in compilers to recognise tokens (keywords like for and if, and variable names).
• You can use prebuilt systems like YACC to build these things.
• They're really fast!
• They're also used in text mining, for quite the same reason.
• I learned about this in my second year computer science degree. The book I used was Elements of the Theory of Computation by Lewis and Papadimitriou. (This is one of say 10 chpts in that book.)