Here we define the language of a DFA, which is the set of all strings that it accepts. Then we look at an example DFA, and try to discern what language it has. We produce some example strings that it accepts, and then see the pattern that it accepts exactly the strings that have a length a multiple of 3 plus 1.

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▶ADDITIONAL QUESTIONS◀
1. Design a DFA with language of all strings w in {0, 1}* that start and end with a 0, or start and end with a 1, or is epsilon. (Super hard: what if w was in {0, 1, 2}*?)
2. Design a DFA with language of all strings in {0, 1}* that contain 111 as a substring.

▶SEND ME THEORY QUESTIONS◀
ryan.e.dougherty@icloud.com

▶ABOUT ME◀
I am a professor of Computer Science, and am passionate about CS theory. I have taught over 12 courses at Arizona State University, as well as Colgate University, including several sections of undergraduate theory.

▶ABOUT THIS CHANNEL◀
The theory of computation is perhaps the fundamental theory of computer science. It sets out to define, mathematically, what exactly computation is, what is feasible to solve using a computer, and also what is not possible to solve using a computer. The main objective is to define a computer mathematically, without the reliance on real-world computers, hardware or software, or the plethora of programming languages we have in use today. The notion of a Turing machine serves this purpose and defines what we believe is the crux of all computable functions.

This channel is also about weaker forms of computation, concentrating on two classes: regular languages and context-free languages. These two models help understand what we can do with restricted means of computation, and offer a rich theory using which you can hone your mathematical skills in reasoning with simple machines and the languages they define.

However, they are not simply there as a weak form of computation--the most attractive aspect of them is that problems formulated on them are tractable, i.e. we can build efficient algorithms to reason with objects such as finite automata, context-f
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https://www.youtube.com/watch?v=D12PEIQhH1A