String Variable in C++

[sonia.sardana]

We can define the variable as string data type or not.

I have read by including the header file string.h, you can declare string type variable.
But my program is having errors:- UNDEFINED SYMBOL STRING

#include<iostream.h>
#include<string.h>
int main()
{
string Name;
name="sonia";
cin.get();
return 0;
}

How can we declare the string variable??