used function defination outside class

/* used scope resolution operator
2.used function defination outside class*/
#include<iostream>
using namespace std;
class demo
{
    public:
        void disp();//declration
};
class demo2
{
    public:
        void show();//declaration
};
void demo::disp()
{
    cout<<"I am disp method of demo class";
}
void demo2::show()
{
    cout<<"I am show method of demo1 class";

}
int main()
{
    demo d1;
    demo2 d2;
    d1.disp();
    d2.show();
}