C/stdlib.h/atexit

    
//Declaration: int atexit(void (*func)(void)); 
//Return:      returns zero if the function is successfully registered as a termination function and nonzero otherwise. 
  

  #include <stdlib.h>
  #include <stdio.h>
  void done(void);
  int main(void)
  {
    if(atexit(done)){
          printf("Error in atexit().");
    }
    return 0;
  }
  void done(void)
  {
    printf("Hello There");
  }
         
/*
Hello There*/