lass Parent{
  public:
    virtual int width();
    virtual int height();
 
};
 
class Child: public Parent{
  int w;
  int h;
  public:
    Child(int a,int b){w=a;h=b;};
    int width(){return w;}
    int height(){return h;}
};
int area(Parent p){return p.width()*p.height();};

Parent* p = new Child(3,4);
 
Child* c = p->VisitChild();[B]//Could you explain in a little bit more detail please? VisitChild() appears not defined. [/B]
 
cout << c->area();

class Parent{
  public:
    virtual int width();
    virtual int height();
   
};
 
class Child: public Parent{
  int w;
  int h;
  public:
    Child(int a,int b){w=a;h=b;};
    int width(){return w;}
    int height(){return h;}
};
template <class T> int area(T){return T.width()*T.

class Parent{
  public:
    virtual int width();
    virtual int height();
    int area(){return width()*height();};
    //[B]Virtual functions are used here to define another function, but this produces an error. [/B] 
//[B]Is is possible to do something like this? [/B]
};

class Child: public Parent{
  int w;
  int h;
  public:
    Child(int a,int b){w=a;h=b;};

void testSwitch(){
  for(int i=1;i<8;i++){
    cout<< i: <<i<< is ;
    switch(i){
      case 1: cout<<1; break;
      case 4: cout<<4; break;
      case 5: cout<<5; break;
      case 6: cout<<6; break;
defaut: cout<<[B]10[/B]; break;
    }
    cout<<endl;
  }
}

void testSwitch(){
  for(int i=1;i<8;i++){
    cout<< i: <<i<< is ;
    switch(i){
      case 1: cout<<1; break;
      case 5: cout<<5; break;
      case 6: cout<<6; break;
      case 4: cout<<4; break;
defaut: cout<<0; break;
    }
    cout<<endl;
  }
}

class complex{
  int x,y;
   ....
  ostream& operator<<(ostream&);//this defines the operator "<<"
  complex& operator/(complex);
}

complex complex::operator/(complex z){
  if ((z==0)){//if divided by 0, print information

#pragma pack(1)

    struct MyStruct
    {
      char data1;
      int data3;
    } ms;
    ms.data1='a';
    ms.data3=0xffffffff;
    FILE*target=fopen("tmp",wb);
    int i=0;
    fwrite(&ms,sizeof(ms),1,target);
    fclose(target);

    struct mp3{//exact copy of MPEGLAYER3WAVEFORMAT 
      WAVEFORMATEX wfx;
      WORD         wID;
      DWORD        fdwFlags;
      WORD         nBlockSize;
      WORD         nFramesPerBlock;
      WORD         nCodecDelay;
    }; 
    cout<<"mp3: "<<sizeof(mp3)<<endl;

typedef struct mpeglayer3waveformat_tag {
  WAVEFORMATEX wfx;
  WORD         wID;
  DWORD        fdwFlags;
  WORD         nBlockSize;
  WORD         nFramesPerBlock;
  WORD         nCodecDelay;
} MPEGLAYER3WAVEFORMAT, *LPMPEGLAYER3WAVEFORMAT;

    cout<<"size of MP3 format: "<<sizeof(MPEGLAYER3WAVEFORMAT)<<endl;