Essential Guide to Digital Signal Processing, The

4. Digital Signals and How They Are Generated

What Is a Digital Signal?

Until the early 1980s, the vast majority of the signals that we experienced in our daily lives, such as light and sound signals, were analog in nature. But the advent of digital clocks, cell phones, portable music players, and digital television has changed much of our world to digital as indicated by Table 1.1 in Chapter 1. So it’s reasonable to ask, “What does the word digital mean? What is a digital signal?” We answer those questions in the following sections.

The Notion of Digital

The development of language is a complicated, and unpredictable, phenomenon. As far as we can tell, our definition of the word digital originated from the notion of counting with your fingers. ...