Analog and digital electronics are an important part of most modern courses in physics. Closely mapped to the current UGC CBCS syllabus, this comprehensive textbook will be a vital resource for undergraduate students of physics and electronics. The content is structured to emphasize fundamental concepts and applications of various circuits and instruments. A wide range of topics like semiconductor physics, diodes, transistors, amplifiers, Boolean algebra, combinational and sequential logic circuits, and microprocessors are covered in lucid language and illustrated with many diagrams and examples for easy understanding. A diverse set of questions in each chapter, including multiple-choice, reasoning, numerical, and practice problems, will help students consolidate the knowledge gained. Finally, computer simulations and project ideas for projects will help readers apply the theoretical concepts and encourage experiential learning. The topics of electronic devices, circuits and systems are broadly classified into two categories: analog and digital, as is also specified in the CBCS curriculum. Maintaining the recommended topics, the subject matters are reorganized so as to facilitate the students. The first introductory chapter outlines briefly the evolution, significance and widespread applications of electronics. Since semiconductors take major part in the fabrication of electronic devices, the subject learning starts with the basic properties and types of semiconductors, electrons and holes, concepts of energy band and effective mass and current transport phenomena (Chapter 2). Chapter 17 presents a brief sketch of the basic principles and architecture of a modern computer and explains in detail the programming technique for Microprocessor 8085. A brief idea is given on Arduino microcontroller system.