Characters

Individual characters in C++ are represented by the built-in primitive data type named char ( usually pronounced "tchar", not "kar"). In memory, these values are represented by assigning each character an 8-bit integer code called an ASCII code . (Actually, only 7-bits are defined by C++, so the ASCII values 128-255 are non-standard and may vary from platform to platform.)

You write character literals by enclosing each character in single quotes. Thus, the literal 'A' represents the internal code of the uppercase letter A.

In addition, C++ allows you to write special characters in a multi-character form beginning with a back-slash (\). This form is called an escape sequence. This includes the newline (\n), the tab (\t), and a double-quote inside a string literal (\"). Here is a list of the C++ escape sequences .

Character Functions

It is useful to have tools for working with individual characters. The <cctype> header contains a variety of functions that do that. There are two kinds of functions.

Predicate classification functions test whether a character belongs to a particular category. Calling isdigit(ch) returns true if ch is one of the digit characters in the range between '0' and '9'. Similarly, isspace(ch) returns true if ch is any of the characters that appear as white space on a display screen, such as spaces and tabs.
Conversion macros make it easy to convert between uppercase and lowercase letters. Calling toupper('a'), for example, returns the character 'A'. If the argument is not a letter, the function returns it unchanged, so that tolower('7') returns '7'.