data type

All variables in C++ must be declared prior to their use. This is necessary because the compiler must know what type of data a variable contains before it can properly compile any statement that uses the variable. In C++ there are seven basic data types: character, wide character, integer, floating point, double floating point, Boolean, and somewhat surprisingly, valueless. The keywords used to declare variables of these types are char, chart, int, float, double, bool, and void, respectively. Common sizes and ranges of each data type are shown in Table 3-1. Remember, the sizes and ranges used by your compiler may vary from those listed here. The most common variance occurs between 16-bit and 32-bit environments. In general, an integer in a 16-bit environment is 16 bits wide. In a 32-bit environment, an integer is usually 32 bits wide Variables of type char are used to hold 8-bit ASCII characters such as A, B, or C, or any other 8-bit quantity. To specify a character, you must enclose it between single quotes. The type wchar_t is designed to hold characters that are part of large character sets. As you may know, many human languages, such as Chinese, define a large number of characters, more than will fit within the 8 bits provided by the char type.