This is 21^st century and we are living in the world of science of technology. At the present context of the world computers have become inseparable part of our life. After the great appreciation of the first, second and third edition of Computer Professional Book-I, we are very happy to present its fourth edition. I am hopeful that the present initiation of Federation of Computer Association Nepal- Kaski (CAN Federation- Kaski) will add one more foundation brick in the field of computer training.  Great endeavors have been undertaken to bring this book in the present form.

I will like to express my gratitude to my collaborate or members. Mr. Sewak Kshitiz and Mr. Achyut Khaniya for their contribution in writing the book. Likewise my  sincere  thanks  goes  to  all  the  member  of  book  publication   subcommittee­ Mr. Biswash Bhandari and Mr. Suresh Sapkota. Similarly I would like to express my sincere thanks to Mr. Anup Adhikari for going through the language section of the book. At the same time Pratik Offset Press also deserves a lot of thanks for undertaking the printing works. Moreover, I appreciate the constructive suggestions from all the members of Publication Sub-committee and all the members of CAN Federation- Kaski.

It’s a great pleasure to present you the updated third edition of Computer Professional Book-I. In spite of great effort to avoid errors you may come across some while using this book. So, I request you all to use this book as a training material and give constructive suggestions for its improvement.

I would like to thank all the students, colleagues and computer professionals who have gone through the first edition and indicated the areas of improvement.

I request all our readers for the constructive suggestions and the feedbacks for improvement of the book.