Using string data type without string header file

Question

The below code shows that a "greeting" function is using "greet" argument with "string" data type without "string" header file

#include <iostream>

using namespace std;

void greeting(string greet, int repeats)
{
for (int i = 0; i < repeats; i++)
cout << greet << endl;
}

int main()
{
greeting("Hi!", 5);
}

how can the code run without identifying the "string" data type?

Answer 1

It's sometime indirectly included by the implementation writers while implementing iostream.
But this is not standard behaviour and thus it's always a good idea to include necessary header in your programs.