Problems Related to Class and Inheritance

To make our ongoing discussion on Inheritance a little more interesting, I have listed some problems or questions here. They all are related to Classes in general and Inheritance in particular.

Problem #1: This program contains some error(s), can you spot which line(s) contains error(s)?

``````
1     // Problems No.1
2     // Related to Inheritance
3     #include<iostream.h>
4
5     // base class
6     class base
7     {
8       int a;
9
10    public:
11      void seta(int num){a=num;}
12    };
13
14    // derived class
15    class derived:public base
16    {
17      int b;
18
19    public:
20      void setb(int num){b=num;}
21
22      void show()
23      {
24        cout<<a<<"\n"<<b;
25      }
26    };
27
28    // main
29    void main()
30    {
31      base b;
32      derived d;
33
34      b.seta(10);
35      d.setb(100);
36
37      d.show();
38    }

``````

Problem #2: This program contains some error(s), can you spot which line(s) contains error(s)?

``````
1     // Problems No.2
2     // Related to Inheritance
3     #include<iostream.h>
4
5     // base class
6     class base
7     {
8     protected:
9       int a;
10
11    public:
12      void seta(int num){a=num;}
13    };
14
15    // derived class
16    class derived:protected base
17    {
18    protected:
19      int b;
20
21    public:
22      void setb(int num){b=num;}
23      void show()
24      {
25        cout<<a<<"\n"<<b;
26      }
27    };
28
29    // main
30    void main()
31    {
32      base b;
33      derived d;
34
35      b.seta(10);
36      d.setb(20);
37
38      d.show();
39
40      b.a=5;
41      d.b=10;
42
43      d.show();
44    }

``````

Problem #3: This program contains some error(s), can you spot which line(s) contains error(s)?

``````
1     // Problems No.2
2     // Related to Inheritance
3     #include<iostream.h>
4
5     // base class (1)
6     class base1
7     {
8     protected:
9       int a;
10    };
11
12    // base class (2) derived from
13    // base1
14    class base2:private base1
15    {
16    protected:
17      int b;
18    };
19
20    // derived from base2
21    class derived:public base2
22    {
23    public:
24      void set(int num1,int num2)
25      {
26        a=num1;b=num2;
27      }
28
29      void show()
30      {
31        cout<<a<<"\n"<<b;
32      }
33    };
34
35    void main()
36    {
37      derived d;
38      d.set(10,20);
39
40      d.show();
41    }

``````

1. Line No. 24

2. Line No. 40 and 41

3. Line No. 26 and 31

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