Question

In VC++ we have the data type “BOOL” which can assume the value TRUE or FALSE, and we have the data type “bool”, which can assume the value true or false.

What is the difference between them and when should each data type be used?

Answer 1

bool is a built-in C++ type while BOOL is a Microsoft specific type that is defined as an int. You can find it in windef.h:

typedef int                 BOOL;

#ifndef FALSE
#define FALSE               0
#endif

#ifndef TRUE
#define TRUE                1
#endif

The values for a bool are true and false, whereas for BOOL you can use any int value, though TRUE and FALSE macros are defined in the windef.h header.

This means that the sizeof operator will yield 1 for bool (the standard states, though, that the size of bool is implementation defined), and 4 for BOOL.

Source: Codeguru article