The keyword boolean indicates that the expression or constant expression associated with the identifier takes the value TRUE or FALSE.
The boolean type is one of the base types of the IDL language. The boolean type can appear as a type specifier in const declarations, typedef declarations, general declarations, and function declarators (as a function-return-type specifier and as a parameter-type specifier). For the context in which type specifiers appear, see IDL.
Note The boolean base type is not compatible with the oleautomation attribute. Use VARIANT_BOOL in your Automation-compatible interfaces.