C++ Code::Blocks undefined #incldue , but string working

Question

I would like to know, how it is possible, that i didn't defined #include string at Code::Blocks and in spite of my variables at date type string still working? I've got TDM-GCC compiler. Thanks

For example this simple code:

#include <iostream>

using namespace std;

int main()
{
  string name;
  int number;
  const int a = 3;

 cout << "Zadej svoje jmeno (bez diakritiky): ";
 getline(cin, name);
 cout << "Zadej cele cislo: ";
 cin >> number;
 cout << "Ahoj, " << name << "." << endl;
 cout << number << " x " << a << " = " << number*a << endl;
 cout << number << " / " << a << " = " << number/a << endl;
  return 0;
}