"Introduction to the Theory of Programming Languages" offers a comprehensive introduction to the design and implementation of programming languages. The book covers the evolution of programming languages from early languages like Fortran and Cobol to modern languages such as Caml and Java. It provides readers with the necessary tools to think about, design, and implement programming languages. The focus is on a unified perspective of the various formalisms used to define programming languages, including small and large steps of operational semantics as well as denotational semantics. These approaches are illustrated through the analysis of typical features of programming languages such as functions, recursion, assignments, and objects. The book demonstrates that the study of programming languages is not isolated but organized around the common characteristics of languages, leading to a deeper insight into the development of evaluators, interpreters, compilers, and type inference algorithms.