The Digital Abstraction
The term a digital circuit refers to a device that works in a binary world. In the binary world, the only values are zeros and ones. In other words, the inputs of a digital circuit are zeros and ones, and the outputs of a digital circuit are zeros and ones. Digital circuits are usually implemented by electronic devices and operate in the real world. In the real world, there are no zeros and ones; instead, what matters is the voltages of inputs and outputs. Since voltages refer to energy, they are continuous (unless quantum physics is used). So we have a gap between the continuous real world and the two-valued binary world. One should not regard this gap as absurd. Digital circuits are only an abstraction ...