The book "Theory of Programming Language" thoroughly examines the subject and various real-world applications of computer technology. Programming language theory is an area of computer science that focuses on the creation, execution, analysis, characterization, and classification of formal programming languages. This comprehensive text introduces the ideas, methods, and sophisticated instrumentation techniques used in programming for beginning computer science students and researchers. This book also provides a reliable study of the programming language and projects its future evolution. It does a fantastic job of giving an overview of the numerous issues addressed in the theory that underpins programming languages. The readers of this handbook can easily understand the fundamental principles that constitute the basis for the philosophy of programming languages. This is because the material is organized and presented in a reader-friendly way. This book is a valuable resource for students, professors, and developers interested in programming language and its theory.