Representing binary data is an intriguing problem. If the binary data represents ASCII, you have no problem displaying it (ASCII is, after all, what you expect when you look at most files). If the file is a program, however, the data most likely can’t be represented as ASCII characters. In that case, you have to display it in some numerical form.

The early minicomputers used 12-bit words. Today, of course, the computer world has settled on the 8-bit byte as the standard unit of memory. Although you can represent data in the familiar decimal (base 10) system, the question becomes what to display—a byte, a word, or 32 bits? Displaying a given number of bits compactly requires that base 2 be raised to the required number of bits. With the old 12-bit systems, you could represent all 12 bits with four numbers (represented by 2³, which was the octal or base 8 format). Because early UNIX systems ran on these kinds of minicomputers, much of the UNIX—and, thus, Linux—notation is in octal. Any byte can be represented by a three-digit octal code that looks like this (this example represents the decimal value of 8):

\010

Because the world has settled on an 8-bit byte, octal is no longer an efficient way to represent data. Hexadecimal (base 16 or 2⁴ ) is a better way. An 8-bit byte can be represented by two hexadecimal digits; a byte whose decimal value is 10 is represented as 0A in hexadecimal.