/in/foo.c: In function 'main':
/in/foo.c:15:12: error: 'size' undeclared (first use in this function)
  int array[size];
            ^~~~
/in/foo.c:15:12: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:17:14: error: 'n' undeclared (first use in this function)
  scanf("%d",&n);
              ^
/in/foo.c:15:6: warning: unused variable 'array' [-Wunused-variable]
  int array[size];
      ^~~~~