Mathematics typically used in the theoretical study of the principles discussed, such as differential equations, Fourier’s theorem, or a significant amount of statistics, is a continuous mathematics that utilizes concepts such as limits, derivatives, integrals, and continuous variables. However, computers cannot use these variables; that must be converted into sequences of numbers called discrete variables. This change entails significant modifications that affect the specific signal acquisition and processing. Therefore, it is important to have a concise overview of the analog-to-digital conversion process. Within this process, the concept of Dirac delta is fundamental to the theoretical processing of signals. Another very important idea is the Nyquist theorem; although this theorem applies in general to all types of signals, both analog and digital, it is time to state it.