/in/foo.c: In function 'main':
/in/foo.c:4:8: error: 'i' undeclared (first use in this function)
  int S[i],c[5],A[5];
        ^
/in/foo.c:4:8: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:4:6: warning: unused variable 'S' [-Wunused-variable]
  int S[i],c[5],A[5];
      ^