Scope Resolution in Class in C++

#include<iostream.h>
#include<conio.h>
class cls //'cls' is name of Class.
{
public:
cls()
{
cout<<"This is Default Constructor of Class cls"<<endl;
}
void fun()
{
cout<<"This is Simple Function of Class cls"<<endl;
}
};
class cls2 //'cls2' is name of another Class.
{
public:
cls2()
{
cout<<"This is Default Constructor of Class cls2"<<endl;
}
void fun()
{
cout<<"This is Simple Function of Class cls2"<<endl;
}
};
void main()
{
 cls obj; //'obj' is object of class 'cls'.
 cls2 obj2; //'obj2' is object of class 'cls2'.
 obj.fun();
 obj2.fun();
 getch();
}

#include<iostream.h>
#include<conio.h>
class cls
{
private:
int a,b;
public:
cls(int x, int y)
{
a = x;
b = y;
}
void show(); //declaring function 'show()'.
};
void main()
{  //calling and passing arguments to parameters and 'obj' is
cls obj(5, 6); //object of class 'cls'.
obj.show(); //calling 'show()' function.
getch();
}
void cls::show() //this is Scope Resolution.
{
cout<<"a is: "<<a<<endl;
cout<<"b is: "<<b<<endl;
}

#include<iostream.h>
#include<conio.h>
class cls
{
private:
static int num; //'num' used for static integer value.
public:
cls() //this is default constructor.
{
num++; //adding 1 to 'num' value.
}
void show()
{
cout<<num<<" Objects is Declared"<<endl;
}
};
int cls::num; //this is Scope Resolution.
void main()
{
cls a, b, c, d, e; //'a, b, c, d and e' is objects of class 'cls'.
e.show(); //calling 'show()' function.
getch();
}