How to use boolean datatype in C?

If you have a compiler that supports C99 you can

#include <stdbool.h>

Otherwise, you can define your own if you'd like. Depending on how you want to use it (and whether you want to be able to compile your code as C++), your implementation could be as simple as:

#define bool int
#define true 1
#define false 0

In my opinion, though, you may as well just use int and use zero to mean false and nonzero to mean true. That's how it's usually done in C.

C99 has a boolean datatype, actually, but if you must use older versions, just define a type:

typedef enum {false=0, true=1} bool;

C99 has a bool type. To use it,

#include <stdbool.h>

As an alternative to James McNellis answer, I always try to use enumeration for the bool type instead of macros: typedef enum bool {false=0; true=1;} bool;. It is safer b/c it lets the compiler do type checking and eliminates macro expansion races