Beginning with the description of operating system in general the book discusses features that made Unix the most suitable operating system of its time. An overview of file management in Unix and commonly used Unix commands is then provided. Further, it delves into the detailed description of file system and compression techniques, processes and signals, vi editor, system calls, and awk scripting. Detailed description about different types of editors and shell programming (including Bourne, C, and interactive Korn shell) has also been provided. Chapters dedicated to debugging and system development, language development, text formatting tools, interprocess communication, and system administration are covered in the later part of the book. To aid students, the book provides numerous examples and complete program scripts that will help in grasping the key concepts effectively. Web Resources: For Students DT Chapter-wise executable and completeshell scripts and codes given in the book DT Mail Organizer - project that sends mail to a desired recipient on a given date. DT Inventory Management System - project that explains maintenance of inventory using MySQL database server DT Debugging exercises with solutions For Faculty DT Chapter-wise PPTs DT Answers to select review exercises given in the book.