Char or Int for boolean value in C?

Question

I find that there is no native bool type. People either use int or char - though it seem that int might be more frequently used than char? Is this true?

My first impulse was to use char as it is a smaller data type, but there something I've missed? Is int better for boolean values, and if so - why?

Answer 1

There is a _Bool in C99, and a bool if you include stdbool.h.

If you don't have it (a decently modern compiler), use int, it's usually the fastest type. The memory savings of using char are likely negligible.

Answer 2

If you're using a reasonably modern C compiler then you just need:

#include <stdbool.h>

This typically has a macro such as:

#define bool _Bool

which lets you use C99's built-in _Bool type wherever you need a bool.

Answer 3

There is a native type named _Bool (starting with C99). In <stdbool.h>, there's also a #define to provide bool as an alias, if you want it (also has #defines for true and false).

Answer 4

Actually there's no real difference since char gets always promoted to int when using it (check this). I have never seen a char used as a bool though, so I'd go for using an int.

Answer 5

According to ISO-9899 the result of relation, logical and equality operators has type int. true and false from stdbool.h are also integers. If you want to spare memory - use bit-fields.