Boolean type ( bool ) is a new basic data type in C++ . The bool type is not defined in the standard C language. If you need to use the bool type, Programmers can customize a bool type through macro definitions. The definition statement is as follows: #define bool int #define false 0 #define true 1 That is, the int type is defined as a bool type, and the two values of the int type are defined as the two values of the bool type, true and false, respectively. But in C ++, there is no need for such trouble, the bool type has been defined in C++. The bool type is one of the basic data structures of the C++ language. On the 80x86 processor, the compiler gcc 4.8.1 and Visual C++ 2012 allocate 1 byte length to the bool type variable. The bool type has only two values: true and false. When doing logical operations, the default non-zero value is true. Defining a bool type variable is also similar to the definition of other primitive data type variables, as follows: bool flag = true;