Suppose we were defining a class that dealt with circles and we wanted a named constant that represented the value p. In most programming languages we would name the constant "pi" because in most languages identifiers (the technical term for names) are limited to the letters and digits available in the ASCII character set. In the Java programming language, however, we can do this:
class Circle
{
static final double p = 3.14159265358979323846;
// ...
}
The Java programming language moves you toward the world of internationalized software: you write code in Unicode, an international character set standard. Unicode basic characters are 16 bits, and together with the supplemental characters (21 bits) provide a character range large enough to write the major languages used in the world. That is why we can use p for the name of the constant in the example. p is a valid letter from the Greek section of Unicode and is therefore valid in source. Most existing code is typed in ASCII, a 7-bit character standard, or ISO Latin-1, an 8-bit character standard commonly called Latin-1. But these characters are translated into Unicode before processing, so the character set is always Unicode.
