The subject of Data Structures is of prime importance for the students of Computer Science and IT. The appropriate data structure is a backbone of any kind of software. It requires a thorough understanding of the basic concepts before putting them into practice. Keeping in mind the requirements of 21 Century, and the academic background of the students, the text of the book is prepared. While preparing the text, special care has been taken to keep the language simple and lucid, and to provide illustrative examples so that even an average reader can grasp the subject matter with quite an ease.