We’ve all heard the cliche that the world of electronic things is “going digital,” but what does that mean? If it’s “going digital,” where is it coming from? What it’s coming from is analog. You may be familiar with the word “analogy” meaning to explain something by comparing it to something more familiar. Analog represents the real world directly. It is continuous and interpolated. We all learned at an early age to read a clock, which is an analog timepiece fashioned after a sundial. The hour hand moves continuously around the face of the clock twice as fast as the sun moves across the sky, and we interpret the position of the hands to tell us the time of day. A phonograph record (remember those?) has a groove on each side (yes, it’s all one long spiral groove) shaped like the recorded sound. The stylus wiggles back and forth in the groove, and it’s attached to a small magnet and coil that puts out a small electric signal that is, again, shaped just like the sound. This signal gets strengthened and sent to the speakers.

Digital, on the other hand, is just numbers. A digital clock represents the time with a discreet number that we read directly. A CD or DVD doesn’t have a groove like a phonograph, it has small pits that represent numbers. These numbers are read by a little computer called a CD player, which converts those numbers to a signal just like the one that comes from the phonograph stylus. Our television broadcasts are going through a similar transition.

So why do this? What’s the advantage? Analog signals need to be shaped very precisely to represent the sound or the image they will reproduce.  They’re very sensitive to distortions and interference. Digital signals, in which numbers are represented by either one or zero, on or off, are more robust and less sensitive. It’s easy to round 1/3 down to zero and 2/3 up to one. In most cases, digital signals either work or they don’t. It’s rare for them to almost work. Also, it’s possible to make them even more robust by adding error-correcting codes that the receiving computer can use to tell that something has gone wrong and, in some cases, fix the problem. Many portable CD players have a switch turns this feature on and off. It lets you listen even though you’re jogging, but drains the battery faster.

Another advantage of analog over digital is that almost any analog recording is degraded by the act of playing it back. It is also almost impossible to copy an analog recording perfectly. A copy of a copy of a copy will eventually be useless. Not so with digital; it’s easy to make an exact copy of a number. This is good news if you want to protect your recording by making a backup or move it from CD to PC to MP3 player, but bad if you want to prevent others from making lots of copies of your work.