Compilare: user.cpp: In function ‘int verif(int)’: user.cpp:34:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<strlen(x);++i) ^ user.cpp: In function ‘int main()’: user.cpp:53:17: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] f>>x[0];x[1]=NULL;nr=0; ^ user.cpp:63:27: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] x[strlen(x)-1]=NULL; ^ user.cpp:71:38: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] l=strlen(x);x[l]=c;x[l+1]=NULL; ^