From cppreference.com
< c‎ | program
Defined in header <stdlib.h>
#define EXIT_SUCCESS /*implementation defined*/
#define EXIT_FAILURE /*implementation defined*/

The EXIT_SUCCESS and EXIT_FAILURE macros expand into integral expressions that can be used as arguments to the exit function (and, therefore, as the values to return from the main function), and indicate program execution status.

Constant Explanation
EXIT_SUCCESS successful execution of a program
EXIT_FAILURE unsuccessful execution of a program

[edit] Example

#include <stdio.h>
#include <stdlib.h>
int main(void)
    FILE *fp = fopen("data.txt","r");
    if (fp == NULL)
       fprintf(stderr,"fopen() failed in file %s at line # %d", __FILE__,__LINE__);
    /* Normal processing continues here. */
    printf("Normal Return\n");
    return EXIT_SUCCESS;


fopen() failed in file main.cpp at line # 9

[edit] See also

C++ documentation for EXIT_SUCCESS, EXIT_FAILURE