#define TRUE !FALSE vs #define TRUE 1

Question

Putting aside the fact that since c99 the stdbool.h has existed, when defining macros to handle Boolean types in C is there any difference between the following

Answer 1

They are just same.

• !0 is 1 so !FALSE is 1

#define TRUE !FALSE has no technical benefit at all although it existed for along time and appeared many where.

#define TRUE !FALSE can be misunderstood, one could think that TRUE represents every value which not 0.

• Only 1 equals to TRUE, others values like 2,3, 255... (which !=0) does not equal to TRUE

To prevent this misunderstanding, many organizations require not using #define TRUE !FALSE any more or comparison to TRUE should be changed to !FALSE:

// Should not     
if (var_bool == TRUE) {
...
}

//Should    
if (var_bool != FALSE) {
...
}