To get an answer to this question you need to take a closer look at diode and transistor circuits. For all the integrated circuits are basically composed of semiconductors. Therefore you should be able to build up the logic circuits with semiconductor components, such as diodes and transistors.
On the following pages you get to know these circuits and build them up. You realize quickly how surprisingly simle these circuits are. In the course you will learn how, by skillfully combining the circuits, you cover all functions of digital electronics.
To get started you need to do a few preparations.