In Dev-C++, you can use string name1, name2 without using include <string>; why?

In Dev-C++, you can use string name1, name2 without using
include <string> ;   why?

For example:

#include <iostream>  
//#include <string>
using namespace std;  
int main() {  
    string s1, s2;  
    cout << "请输入两个字符串：";
    cin >> s1 >> s2;
    cout << "排序结果：";  
    if(s1 < s2)  
        cout << s1 << "," << s2;  
    else  
        cout << s2 << "," << s1;  
        
    return 0;  
}

Compile and run

In C++, the string type is defined in the <string> header file. Generally, if you want to use the string type in your code, you need to include the <string> header file. However, in some cases, you may find that your code still works fine even without explicitly including <string>. This is because other header files (such as <iostream>) may already include <string>, however, this behavior is not standardized.
Because not all compilers do this, it is best to include the <string> header explicitly to ensure code portability and stability.
If your code uses strings, it is recommended to include the <string> header file, which can clearly express "explicitly following the standard C++ specification". This makes your code easier to understand and avoids problems with different compilers or settings.