This book entitled "COMPUTER APPLICATION IN BUSINESS" covers DATA COMMUNICATIONS AND NETWORKING, OPERATING SYSTEMS, MS OFFICE, and MIS which are considered to be the most important packages for a business. There are many specialized packages/softwares for administering the business, but MS OFFICE is user friendliness. The approach of authors in handling this subject is as simple as a nutshell. This book is very lucid and elaborate to facilitate the student''s for improving their practical knowledge and elucidation of the same were also given at appropriate chapters. Shortcut keys were also given for effective operation. This book is fragmented into 25 Lessons which covers the syllabus for Commerce Graduates and Post Graduates and business Professionals. We hope this book will be handy and helping source to those who pursue it to escalate their computer operating skills in business and its related activities.