Question

I have this program execute with the values 10,20,30 given at command line.

int main(int argc , char **argv)
 { 
  printf("\n Printing the arguments of a program \n");
  printf("\n The total number of arguments in the program is %d",argc);
   while(argc>=0)
    { 
     printf("%s   ",argv[argc]);
     argc--;
     }
     return 0;
  }    

The outputs is
The total number of arguments in the program is 4(null) 30 20 10 ./a.out

Where did that (null) come from ??

Answer 1

argv[0] is (to the extent possible) supposed to be something that identifies the program being run. argv[1] through argv[argc-1] are the arguments that were actually entered on the command line. argv[argc] is required to be a null pointer (§5.1.2.2.1/2).