虚函数和函数重载的问题

#include <iostream>
using namespace std;

class A
{
public:
    int fun(int a){return a;}
    int fun(int a,int b){return a+b;}
    virtual float fun(float c){return c;}
    virtual void f()=0;//纯虚函数
};

class B:public A
{
public:
    int fun(int a)
    {
        return a+10;
    }
    int fun(int a,int b)
    {
        return a+b+10;
    }
    float fun(float c)
    {
        return c+10.0;
    }
    void f()
    {
        cout<<"子类不重写纯虚函数，父类不能实例化，且子类继承父类必须实例化纯虚函数"<<endl;
    }
};

class C
{
public:
    C() {}
    ~C() {}
    int f;
};

/*函数的重载*/
int fun(int a)
{
    return a;
}

int fun(int a,int b)
{
    return a+b;
}

float fun(float a)
{
    return a;
}

int main()
{
    int a=fun(1);
    int b=fun(1,2);
    float c=1.23;
    float d=fun(c);
    cout<<a<<‘ ‘<<b <<‘ ‘<<d<<endl;

//    A aa;拥有纯虚函数，不能初始化
    A *aa=new B;
    cout<<aa->fun(1)<<‘ ‘<<aa->fun(1,2)<<‘ ‘<<aa->fun(float(1.23))<<endl;
    B *bb=new B;
    cout<<bb->fun(1)<<‘ ‘<<bb->fun(1,2)<<‘ ‘<<bb->fun(float(1.23))<<endl;
    aa->f();
    bb->f();

    C cc;//申请的空间里的值是随机值
    cout<<cc.f<<endl;
    C *ccc=new C();//申请的空间里的值已经初始化
    cout<<ccc->f<<endl;
    return 0;
}