Overloading << error - c++

Question

I am kind of newbie to programming migrated from legacy turbo c++ to VS C++2012,I have a tough time catching up and i wanted to emulate the string library for TC. But i cant make the insertion operator work in this code....Please help Out. Could you tell the mistake i made in this code. And also why are we returning the object via reference for overloading.
#include<iostream>
#include<string>
namespace String
{
class string
{
char word[100];
int size;
public:
string()
{
size=0;
}
string(int sz)
{
size=sz;
}
string(char *Word)
{
strcpy(word,Word);
size=sizeof(*Word);
}
~string()
{
}
string &operator+(string Add)
{
strcat(word,Add.word);
return *this;
}
string &operator=(char *Word)
{
strcpy(word,Word);
return *this;
}
/*
ostream &operator<<(ostream &sout,string Show)
{
sout<<Show.word;
return sout;
}
*/
void Show()
{
std::cout<<word;
}
};
}
void main()
{
String::string A="ABCDEF";
String::string B="GHIJK";
String::string C;
C=A+B;
C.Show();
std::cin.ignore(2);
//std::cout<<C;
}

Answer 1

You should declare operator<< as a non-member function, because ostream will be taken as the 1st argument for operator<<, a user define type's member function can't satisfy it.
namespace String
{
class string
{
...
public:
ostream& put(ostream &sout) { sout << word; return sout; }
};
ostream& operator<<(ostream& sout, string Show) { return Show.put(sout); }
}

Answer 2

The output operator << has to be overloaded in the namespace, not the class itself if you want to be able to use it like so:
cout << my_class_object;
So, in the declaration of your class (string.h) add this line:
ostream &operator<<(ostream & sout,const string & Show);
And then in the definition file (string.cpp) in your namespace, not the class itself, ad this function:
ostream & operator<<( ostream & out, const bigint & data )
{
// the printing implementation
}