What is the difference between BOOL and bool?
Solution 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
Solution 2
Windows API had this type before bool
was thrown into C++. And that's why it still exits in all Windows function that take BOOL. C doesn't support bool
data-type, therefore BOOL
has to stay.
Solution 3
To add to what luvieere has said, you can return something other than TRUE
or FALSE
from a function returning a BOOL
e.g.,
BOOL myFunc(int a)
{
if (a < 3) return FALSE;
else if (a > 3) return TRUE;
else return 2;
}
And this is possible because a BOOL
is essentially an int
.
Please note that this is not advisable as it severely destroys the general readability of code but it is something you can come across and you will be wondering why it is so.
Umesha MS
Updated on July 09, 2022Comments
-
Umesha MS almost 2 years
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?
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user1703401 almost 13 yearssizeof(BOOL) is still 4 on a 64-bit Windows machine. Isolating itself from the compiler type implementations is the reason these typedefs exist.
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luvieere almost 13 years@Hans Removed the 64-bit reference.
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Mark Ransom almost 13 years+1 for pointing out that this is a really bad idea. The whole reason to use BOOL is to restrict the values to TRUE/FALSE; if you want
int
you should useint
. -
eFloh about 10 yearsWARNING: sizeof(bool) is not specified in microsoft c++ and changed from 4 bytes to 1 byte between c++ 4.2 and 5.0 (see msdn.microsoft.com/en-US/en-use/library/tf4dy80a.aspx)
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PeterAllenWebb about 9 yearsThe C99 standard does include a bool type, though it's definitely true that most C compilers did not support bool until relatively recently.
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Marc Durdin over 3 yearsMany (but not all) Windows API functions treat any non-zero
BOOL
asTRUE
. Because this behaviour is not consistent, you should always explicitly useTRUE
(i.e.1
) and not non-zero. This can be tricky because some languages defineTrue
as all bits set (-1
for signed integers) -
Turret about 3 yearsIf you want the C++ like bools in Standard C, #include <stdbool.h>