A Boolean variable can be used to hold the integer values 0 or 1, , which are implicitly promoted to the integers 1 and 0 respectively, whenever an arithmetic value is necessary. The Boolean type is unsigned and has the lowest ranking in its category of standard unsigned integer types; it may not be further qualified by the specifiers signed, unsigned, short, or long. In simple assignments, if the left operand is a Boolean type, then the right operand must be either an arithmetic type or a pointer.
Boolean type is a C99 feature. To declare a Boolean variable, use the _Bool type specifier.
The token bool is
recognized as a keyword in C only when used in a vector declaration
context and vector
support is enabled. 
You can use Boolean types to make Boolean logic tests.
A Boolean logic test is used to express the results of a logical operation.
For example:
_Bool f(int a, int b)
{
return a==b;
}