#include <iostream.h>
int main()
{
int a;
cout<<"请输入一个数字，按回车结束"<<endl;
cin>> a;
cout<<a<<endl;
return 0;
}

在编译时会出现如下提示:

:\lxc\study\l.c(5) : error C2065: 'cout' : undeclared identifier
d:\lxc\study\l.c(5) : error C2297: '<<' : illegal, right operand has type 'char [27]'
d:\lxc\study\l.c(5) : error C2065: 'endl' : undeclared identifier
d:\lxc\study\l.c(6) : error C2065: 'cin' : undeclared identifier
d:\lxc\study\l.c(6) : warning C4552: '>>' : operator has no effect; expected operator with side-effect
d:\lxc\study\l.c(7) : warning C4552: '<<' : operator has no effect; expected operator with side-effect