This book is a comprehensive practical guide to the design, development, programming, and construction of compilers. It details the techniques and methods used to implement the different phases of the compiler with the help of FLEX and YACC tools. The topics in the book are systematically arranged to help students understand and write reliable programs in FLEX and YACC. The uses of these tools are amply demonstrated through more than a hundred solved programs to facilitate a thorough understanding of theoretical implementations discussed.