What are some specific applications of finite state automata? [closed]

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There are several topics discussing finite state automata, but none that I've seen that go into detail about real world applications. What are 开发者_高级运维some concrete examples of finite state automata in action?

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Most popular application of FSMs are parsers of various kind.

As for real life example is my markup (HTML/XML) parser (tokenizer to be precise): HTML_XML_Scanner