This book is designed for undergraduate students to lay a foundation for assembly language programming with 8051 micro-controller. It contains basic principles, pin description, format of special function registers, instruction set and its classification. The main focus of this book is to inculcate the interest for assembly language programming. A systematic, step by step approach is used to understand the assembly language programming. This book contains six chapters and two appendixes.Each chapter includes programs (written in assembly language),review questions and exercise questions.