Say you want to sing into a microphone. You can easily amplify the sound of your voice to reach the ears of hundreds more people than you could have without it. Have you ever stopped to think though, how does a microphone work?
Sound starts off as a sound wave, but when projected into a microphone becomes an electrical wave. This transition is the process of sound becoming digitized. Microphones are an analog system, so the production of noise (as in extra unwanted sounds) is possible, but it is impossible to determine what is noise and what is just being produced by the microphone.
When the telephone was created in 1876 by Alexander Graham Bell, it underwent a similar, analog, process where the sound waves hit a thin metal plate that moved a magnet + wire, creating an electrical current that varied continuously through wires until reaching another phone, where the process was then reversed. The drawbacks of this system was that it, again, produced noise- unwanted sounds, often static.
Telephones did not become digitized until the late 1960s with Pulse Code Modulation, which sampled sounds, quantized them into numerical values and then encoded in a binary form to be sent over a network. This is what allows us to have the quality of calls we have today.
This binary system is also what allows us to digitize text. Each character such as ‘A’ or ‘B’ has a number associated with it that can be displayed through binary code. For example, ‘A’ = 65, which in binary is 01000001. Computers utilize this system to produce letters and words without having the “noise” of an analog system because the system only has the differentiate between a 0 and a 1.