Compilare: user.cpp: In function ‘int main()’: user.cpp:10:7: warning: left operand of comma operator has no effect [-Wunused-value] if ( c>='a',c <='z' || c>='A',c <='Z' ){ ^ user.cpp:10:35: warning: right operand of comma operator has no effect [-Wunused-value] if ( c>='a',c <='z' || c>='A',c <='Z' ){ ^