Recently discovered that some compilers (such as a friend with vs2010) prompted the use of this type bool write functions when the compiler does not recognize this type, checked and found that some compilers believe that this type bool insecure, they want a you can replace the wording of bool, who look to white
BOOL define a called enumeration method (upper bool facilitate recognition) enumeration, enumeration using default the first enumeration member 0, the subsequent enumeration member integer value of a previous this feature adds 1 to the members, with the return value of type bool false (0), and to true (1), whereby the purpose of bool custom implementation.