Question

According to the text at http://www.cplusplus.com/reference/string/string/, string library in C++ is a class, not just a ” mere sequences of characters in a memory array”.
I wrote this code to find out more:

string s = "abcd";

cout << &s << endl; // This gives an address
cout << s[0] << endl; // This gives 'a'
cout << &s[0] << endl; // This gives "abcd"

I have some questions:
1. Is string library in C++ still an array of sequence characters?
2. How can I get the address of each character in string? (As in the code, I can retrieve each character, but cannot get its address using & operator)

Answer 1

Much (most) of this really isn’t about the string class itself.

std::string does store its contents as a contiguous array of characters.

&s[0] will yield the address of the beginning of that array — but std::ostream has an overload of operator<< that takes a pointer to char, and prints it as a string.

If you want to see the addresses of the individual characters in a string, you need to take their addresses and then cast each address to pointer to void. std::iostream also has an overload of operator<< that takes a pointer to void, and that overload prints out the address instead of a string that (it assumes) is at that address.

Edit: demo code:

#include <iostream>
#include <string>

int main(){
    std::string x("this is a string");

    std::cout << &x[0] << "\n";
    std::cout << (void *)&x[0] << '\n';
    return 0;
}

Result:

this is a string
00481DE0