This Book titled "Introduction to Theory of Automata & Compiler Design" is a beginner's guide for Students of Computer Science and Engineering to learn the basics of two subjects namely Theory of Computation and Compiler Design. Theory of Computation lays the foundation for designing complex software such as Compiler and Word Processor. With the help of design notations such as Finite Automata, Regular Expressions and Context Free Grammar, a Software Engineer can design Lexical Analyzer and Parser, two components of a Compiler.