4.12 Boolean Type

The bool type can hold the value true or false. For example:

bool flag; /* Flag can be on or off */
flag = true; 

This type of variable is extremely useful when dealing with logic statements, as described in Chapter 6.

Legacy Boolean Types Until recently the C language did not have a bool [4] type. Because of this, people used macros and the typedef statements to define their own boolean type. Most of the time they called it BOOL, or sometimes Bool. You may see these types in old (and not so old) programs. These names are depreciated and should not be used in current C++ programs.

^[4] Yes, C does have a bool type. See the C standard: ISO/IEC 9899:1999(E) section 7.16.