Compilare: user.c: In function ‘main’: user.c:15: warning: array subscript has type ‘char’ user.c:15: warning: array subscript has type ‘char’ user.c:15: warning: array subscript has type ‘char’ user.c:18: warning: array subscript has type ‘char’ user.c:18: warning: array subscript has type ‘char’ user.c:18: warning: array subscript has type ‘char’ user.c:18: warning: array subscript has type ‘char’ user.c:18: warning: operation on ‘j’ may be undefined user.c:18: warning: operation on ‘j’ may be undefined user.c:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:10: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:11: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:12: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:17: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result