Why do we have multiple declarations for main in C?

C does not support function overloading. How can we then have 3 prototypes for main? What is the historical reason for havin开发者_运维技巧g 3 prototypes?

There are only two prototypes for main that a standard-conforming C implementation is required to recognize: int main(void) and int main(int, char *[]). This is not overloading, since there can still only be one main per program; having a void foo(int, double) in one program and a char *foo(FILE *) in another isn't overloading either.

The reason for the two prototypes is convenience: some applications want command-line arguments, while others don't bother with them.

All other prototypes, such as void main(void) and int main(int, char *[], char *[]), are compiler/platform-dependent extensions.