4. Constants

We have already seen decimal integer constants in the previous example — 1, 2, and 3. Since C is often used for system programming and bit-manipulation, octal numbers are an important part of the language. In C, any number that begins with 0 (zero!) is an octal integer (and hence can’t have any 8’s or 9’s in it). Thus 0777 is an octal constant, with decimal value 511.

A ``character’’ is one byte (an inherently machine dependent concept). Most often this is expressed as a character constant, which is one character enclosed in single quotes. However, it may be any quantity that fits in a byte, as in flags below:

char quest, newline, flags;

quest = ‘?’;

newline = ‘\n’;

flags = 077;

The sequence `\n’ is C notation for ``newline character’’, which, when printed, skips the terminal to the beginning of the next line. Notice that `\n’ represents only a single character. There are several other ``escapes’’ like `\n’ for representing hard-to-get or invisible characters, such as `\t’ for tab, `\b’ for backspace, `\0’ for
end of file, and `\\’ for the backslash itself.

float and double constants are discussed in section 26.