/in/foo.cc: In function 'int main()':
/in/foo.cc:7:10: error: 'i' was not declared in this scope
  int arr[i][j];
          ^
/in/foo.cc:7:13: error: 'j' was not declared in this scope
  int arr[i][j];
             ^
/in/foo.cc:12:17: error: 'arr' was not declared in this scope
    printf("%4d",arr[i][j]);
                 ^~~