This book on "Operating Systems" is written for the students of V Semister B.E., CSE/ISE, III Semester MCA and BCA, covering the syllabus of engineering students from Chapter 1 to 11; For MCA from Chapter 1 to 9 and Chapter 13; for BCA the chapters are from Chapter 1 to 9 and Chapter 12. This book covers V. T. U. syllabus completely. Example problems are solved and explained in steps wherever required. At the end of every chapter exercise questions are provided.