[C++] Operator overloading Part2

#include<iostream>
#include<cstring>
#define MAX_STRING 100
using namespace std;
class myString
{
    friend istream& operator >> (istream&, myString&);
    friend ostream& operator << (ostream&, myString&);
    private:
        char content[MAX_STRING];
    public:
        char operator [] (int);
        myString operator += (myString);
};
istream &operator >> (istream &in, myString &temps)
{
    in >> temps.content;
    return in;
}
ostream &operator << (ostream &out, myString &temps)
{
    out << temps.content;
    return out;
}
char myString::operator [] (int n)
{
    return content[n];
}
myString myString::operator += (myString s)
{
    strcat_s(content, s.content);
    return *this;
}
int main()
{
    myString s1,s2;
    cin >> s1 >> s2;
    cout << s1[0]<<endl;
    cout << (s1 += s2) << endl;
    system("pause"); 
    return 0;
}