Lesson 25 -C-Constants

Lesson 25 -C-Constants

A C constant is usually just the written version of a number. For example 1, 0, 5.73, 12.5e9. We can specify our constants in octal or hexadecimal, or force them to be treated as long integers.

Octal constants are written with a leading zero - 015.
Hexadecimal constants are written with a leading 0x - 0x1ae.
Long constants are written with a trailing L - 890L.
Character constants are usually just the character enclosed in single quotes; 'a', 'b', 'c'. Some characters can't be represented in this way, so we use a 2 character sequence.

'\n' newline
'\t' tab
'\\' backslash
'\'' single quote
'\0' null (used automaticall to terminate character strings).

In addition, a required bit pattern can be specified using its octal equivalent.

'\044' produces bit pattern 00100100.

Character constants are rarely used, since string constants are more convenient. A string constant is surrounded by double quotes eg "Brian and Dennis". The string is actually stored as an array of characters. The null character '\0' is automatically placed at the end of such a string to act as a string terminator.

A character is a different type to a single character string. This is important.

We will meet strings and characters again when we deal with the input / output functions in more detail.