Mid-Term Exam (2)
C++ Programming
NCNU CSIE

Date: April 14th, 2010
Time: 14:10-16:00
Open book; turn off computer & mobile phone

1. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   

   // Accessing Private Class Members
   #include <iostream>
   using std::cout;
   class CNumber
   {
           int n;
   
   public:
           CNumber(int i=0): n(i) {}
           void Set(int i) { n=i; }
           int Get() { return n; }
   };
   
   int main()
   {
           CNumber N1(1);
           N1.Set(5);
           cout << N1.Get() << "\n";
   }
   

2. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   
   // Const Member Function
   #include <iostream>
   using std::cout;
   class CNumber
   {
           int n;
   
   public:
           CNumber(int i=0): n(i) {}
           void Set(int i) const
                   { n=i; }
           int Get() { return n; }
   };
   
   int main()
   {
           CNumber N1(1);
           N1.Set(5);
           cout << N1.Get() << "\n";
   }
   
   
   
3. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   
   // Copy Constructor
   #include <iostream>
   using std::cout;
   
   class CBox {
   
   public:
      int weight;
   
      CBox(int w=0) : weight(w)
      { cout << "Constructor called.\n"; }
      CBox(CBox& aBox)
      { cout << "Copy Constructor called.\n";
        this->weight = aBox.weight + 5;
      }
   };
   
   int main()
   {
      CBox box1(10);
      CBox box2; box2 = box1;
      CBox box3 = box1;
      cout << box2.weight << "\n";
      cout << box3.weight << "\n";
   }
   
   
   
4. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   

   // Operator Overloading
   #include <iostream>
   using std::cout;
   class CRectangle
   {
           int left, top, right, bottom;
   
           int Area() const
           { return (right-left)*(bottom-top); }
   public:
           CRectangle(int x1, int y1, int x2, int y2): 
   		left(x1), top(y1), right(x2), bottom(y2) {}
           bool operator>(const CRectangle& aRect) const
           { return Area() > aRect.Area(); }
   };
   
   int main()
   {
           CRectangle pool(10, 20, 30, 50);
           CRectangle hut(20,30, 45, 50);
           if (pool > hut)
                   cout << "The pool is bigger.\n";
           else
                   cout << "The hut is bigger.\n";
   }
   

5. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   
   // Destructor
   #include <iostream>
   using std::cout;
   class CNumber
   {
           int value;
           char* name;
   
   public:
           CNumber(int n = 0, char* str = "Zero"): value(n)
           {
                   name = new char[strlen(str) + 1];
                   strcpy(name, str);
           }
           ~CNumber()
           {
                   cout << "Destroying " << name << " with value " << value << "\n";
                   delete[] name;
           }
   };
   
   int main()
   {
           CNumber n0;
           CNumber n5(5, "Five");
   }
   


6. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   
   // Overloading the Decrement Operator
   #include <iostream>
   using std::cout;
   
   char* Digits[] = { "Zero", "One", "Two", "Three", "Four",
                       "Five", "Six", "Seven", "Eight", "Night" };
   
   class CNumber
   {
           int value;
           char* name;
   
   public:
           CNumber(int n = 0): value(n)
           { name = Digits[n];     }
           CNumber& operator--()   // Prefix decrement operator
           {
                   --value;
                   return *this;
           }
           void Show()
           { cout << name << "\n"; }
   };
   
   
   int main()
   {
           CNumber i(5);   i.Show();
           --i; i.Show();
   }
   


7. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   
   // Derived Class
   #include <iostream>
   using std::cout;
   
   class CBox
   {
   
           int m_Length;
           int m_Width;
           int m_Height;
   
   public:
           CBox(int lv, int wv, int hv): m_Length(lv), m_Width(wv), m_Height(hv) { }
           int Volume() { return m_Length * m_Width * m_Height; }
   };
   
   class CCandyBox: protected CBox
   {
   private:
           char m_Contents[20];
   public:
           CCandyBox(int lv, int wv, int hv, char* str = "Candy"): CBox(lv, wv, hv)
           { strcpy(m_Contents, str); }
   };
   
   int main()
   {
           CCandyBox myCandy(2, 3, 4, "Wafer");
           cout << myCandy.Volume() << '\n';
   }
   
   
   
   
8. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   
   // Friend Function
   #include <iostream>
   using std::cout;
   
   class CBox
   {
           int m_Length;
           int m_Width;
           int m_Height;
   
   public:
           CBox(int lv, int wv, int hv): m_Length(lv), m_Width(wv), m_Height(hv) { }
           int Volume() { return m_Length * m_Width * m_Height; }
   };
   
   class CCandyBox: protected CBox
   {
   private:
           char m_Contents[20];
   public:
           CCandyBox(int lv, int wv, int hv, char* str = "Candy"): CBox(lv, wv, hv)
           { strcpy(m_Contents, str); }
   friend int main();
   };
   
   int main()
   {
           CCandyBox myCandy(2, 2, 2, "Mint");
           cout << myCandy.Volume() << '\n';
   }
   
   
   
9. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   
   // Virtual Function
   #include <iostream>
   using std::cout;
   
   class Window // Base class for C++ virtual function example
   {
     public:
        void Create() // virtual function for C++ virtual function example
        {
             cout << "Base class Window\n";
        }
   };
   
   class CommandButton : public Window
   {
     public:
        void Create()
        {
            cout<<"Derived class Command Button - Overridden C++ virtual function\n";
        }
   };
   
   void main()
   {
       Window  *x, *y;
   
       x = new Window();
       x->Create();
   
       y = new CommandButton();
       y->Create();
   }
   
   
   
10. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is
    incorrect, point out the mistake(s).
    
    
    // C++ Preprocessor Directives
    #include <iostream>
    using std::cout;
    #define         AAA     5
    #define         F(x)    printf("The value of " #x " is %d.\n", x)
    int main()
    {
            int i;
            for (i=0; i<AAA; i++)
                    ;
            F(i);
    }