Digital Circuits We live in a digital world. Everything is digitalized. All these have been made possible by the advent of computers which deal with binary digits. Computer has invaded every sphere of our lives. The heart of a computer is the microprocessor. A microprocessor incorporates the functions of a computer's central processing unit (CPU) on a single integrated circuit (IC), or at most a few integrated circuits. It is a multipurpose, programmable, clock-driven, register-based electronic device that accepts binary data as input and processes data according to the given instructions, and provides results as output. This introductory text is primarily designed for the average class of students who are interested to know the basics of digitally-controlled devices. It deals with the different parts of a microprocessor in a simple way. Nutan Lata is presently an Assistant Professor in the Department of Physics, Doranda College, Ranchi university, Ranchi, India. She has published a number of research papers and has attended a number of conferences. She is Life Member of Institution of Electronics and Telecommunication Engineers (IETE), New Delhi, India.