Hello gurus,

I would like to ask a very basic question about C++ class. I have been reading teach yourself c++ in 21 days. One of the Q&As of day6(basic classes) is as the following:

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Q: If I declare a class Cat with a private member itsAge and then define two Cat objects, Frisky and Boots, can Boots access Frisky's itsAge member variable?

A: Yes. Private data is available to the member functions of a class,and different instances of the class can access each other's data. In other words, if Frisky and Boots are both instances of Cat, Frisky's member functuions can access Frisky's data and also Boots's data.

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I understand the first half of the explanation which is "Private data is available to the member functions of a class". I am confused about the second part which is " different instances of the class can access each other's data".

If I create two objects(Frisky and Boots) on stack, they have two different memory addresses for their own variable. It is itsAge in this case. It's true that Frisky's member functuions can access Frisky's data. But why Frisky's member functuions can also access Boots's data?

I thought the only way to access Boots's data is to use something like Boots.GetAge().

The simple test program is as following:

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#include <iostream>
using namespace std;

class Cat
{

public:
Cat();
~Cat();
void SetAge(int age) { itsAge=age;}
int GetAge() { return itsAge;}

private:

int itsAge;

};

Cat::Cat()
{
cout<<"Constructor called.\n";
itsAge=1;

}

Cat::~Cat()
{

cout<<"Destructor called.\n";


}

int main()
{
Cat Frisky;
Cat Boots;

Frisky.SetAge(10);
Boots.SetAge(8);

cout<<Frisky.GetAge()<<endl;
cout<<Boots.GetAge()<<endl;


return 0;

}

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I just don't know how to write to make Frisky access Boots's age. Could you please add some lines in my test program to do so?

Thank you very much for your time!

Sincerely,
yahoo