Compilare: user.cpp: In function 'int verif(int, char)': user.cpp:10: warning: comparison between signed and unsigned integer expressions user.cpp:19: warning: comparison between signed and unsigned integer expressions user.cpp:32: warning: comparison between signed and unsigned integer expressions user.cpp:7: warning: unused variable 'i' user.cpp:7: warning: unused variable 'a' user.cpp:7: warning: unused variable 'x1' user.cpp: In function 'int main()': user.cpp:55: warning: converting to non-pointer type 'char' from NULL user.cpp:60: warning: converting to non-pointer type 'char' from NULL user.cpp:63: warning: converting to non-pointer type 'char' from NULL user.cpp:67: warning: converting to non-pointer type 'char' from NULL user.cpp:69: warning: comparison between signed and unsigned integer expressions user.cpp:73: warning: converting to non-pointer type 'char' from NULL user.cpp:59: warning: 'k' is used uninitialized in this function