Code: The Hidden Language of Computer Hardware and Software

This table shows the letters that result from each particular consecutive sequence of dots and dashes. To decode a particular sequence, follow the arrows from left to right. For example, suppose you want to know which letter corresponds to the code dot-dash-dot. Begin at the left and choose the dot; then continue moving right along the arrows and choose the dash and then another dot. The letter is R, shown next to the last dot.

Chapter 2. Codes and Combinations

"Memory is like the surface of your desk and storage is like the filing cabinet."

The word bit, coined to mean binary digit, is surely one of the loveliest words invented in connection with computers.

Chapter ​​​​​2. ​​​​​Codes and Combinations

For example, when we talk to another person, every word we speak is a choice among all the words in the dictionary. If we numbered all the words in the dictionary from 1 through 351,482, we could just as accurately carry on conversations using the numbers rather than words.

As I feared, the reactions weren't favorable. "Oh, I have a book like that," some people would say, to which my immediate response was, "No, no, no, you don't have a book like this one."

A 4-bit processor can add 32-bit numbers, for example, simply by doing it in 4-bit chunks. In one sense, all digital computers are the same. If the hardware of one processor can do something another can't, the other processor can do it in software; they all end up doing the same thing. This is one of the implications of Alan Turing's 1937 paper on computability.

This is the result of an engineering principle known as TANSTAAFL (pronounced tans toffle), which means "There Ain't No Such Thing As A Free Lunch." Usually, whenever you make a machine better in one way, something else tends to suffer as a result.

You'll recall from Chapter 13 that you can use two's complements to represent negative numbers.