/in/ex1.c: In function 'main':
/in/ex1.c:7:10: error: unused variable 'a' [-Werror=unused-variable]
     char a[600][30] = {0};
          ^
/in/ex1.c:6:14: error: unused parameter 'argc' [-Werror=unused-parameter]
 int main(int argc, char *argv[]) {
              ^~~~
cc1: all warnings being treated as errors