请教一下我写的编程的问题有哪些？

请教一下我写的编程的问题有哪些？运行是错误的。主函数那里不会写

#include <iostream>
using namespace std;

class CPU 
{
public:
    CPU() { cout << __FUNCTION__ << endl; };
    ~CPU() { cout << __FUNCTION__ << endl; };
};

class RAM
{
public:
    RAM() { cout << __FUNCTION__ << endl; }
    ~RAM() { cout << __FUNCTION__ << endl; }
};

class CDROM 
{
public:
    CDROM() { cout << __FUNCTION__ << endl; }
    ~CDROM() { cout << __FUNCTION__ << endl; }
};

class Computer
{
    CPU cpu;
    RAM ram;
    CDROM cdrom;
public:
    Computer() { cout << __FUNCTION__ << endl; }
    ~Computer() { cout << __FUNCTION__ << endl; }

    void start() { cout << __FUNCTION__ << endl; }
    void stop() { cout << __FUNCTION__ << endl; }
};

int main()
{
    Computer computer;
    computer.start();
    computer.stop();

    system("pause");
    return 0;
}