Compilare: user.c: In function ‘prec_’: user.c:42:7: warning: array subscript has type ‘char’ [-Wchar-subscripts] ok[a] = ok[a ^ 0x20] = 1; ^ user.c:44:7: warning: array subscript has type ‘char’ [-Wchar-subscripts] ok[a] = 1; ^ user.c: In function ‘input’: user.c:52:12: warning: array subscript has type ‘char’ [-Wchar-subscripts] for (; ok[*cur]; ++cur); ^ user.c:54:13: warning: array subscript has type ‘char’ [-Wchar-subscripts] for (; !ok[*cur]; ++cur); ^ user.c: In function ‘main’: user.c:64:3: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(InFile, "r", stdin); ^ user.c:65:3: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(OuFile, "w", stdout); ^