problem in inherting class in dev c++

i made a program in dev c++ to calculate salary of regular based employee and hourly based employee but when i compile the program i got some errors. i want to inherit person class in both re and hbe class but the problem is that the function definitions for input();calsalary() and display() are different for the child classes.

error- no `void re::input()' member function declared in class `re'
same for other member functions also

Code:

#include<iostream>
#include<conio.h>
using namespace std;

class person
{
   protected:
    char ch[20];
 
   public:
     void input();
     float calsalary();
     void display();
};

class re:public person
{
   int empid;
   float basic,da,hra,pf; 
};

class hbe:public person
{
   int empid,hpm;
   float pph;
};

void re::input()
{
     cout<<"\n Name      = ";
     cin>>ch;
     cout<<"\n Emp ID    = ";
     cin>>empid;
     cout<<"\n Basic pay = ";
     cin>>basic;
     cout<<"\n DA        = ";
     cin>>da;
     cout<<"\n HRA       = ";
     cin>>hra;
     cout<<"\n PF        = ";
     cin>>pf;
}

float re::calsalary()
{
      return(basic+da+hra+pf);
}

void re::display()
{
     cout<<"\n Name       = "<<ch;
     cout<<"\n Emp ID     = "<<empid;
     cout<<"\n DA         = "<<da;
     cout<<"\n HRA        = "<<hra;
     cout<<"\n PF         = "<<pf;
     cout<<"\n Net Salary = "<<calsalary();
}    

void hbe::input()
{
     cout<<"\n Name            = ";
     cin>>ch; 
     cout<<"\n Emp ID          = ";
     cin>>empid;
     cout<<"\n Pay per hour    = ";
     cin>>pph;
     cout<<"\n Hours per month = ";
     cin>>hpm;
}

float hbe::calsalary()
{
      return(pph*hpm);
}

void hbe::display()
{
     cout<<"\n Name       = "<<ch;
     cout<<"\n Emp ID     = "<<empid;
     cout<<"\n Hr per mon = "<<hpm;
     cout<<"\n Pay per Hr = "<<pph;
     cout<<"\n Net Salary = "<<calsalary();
}    

int main()
{
    re  o1;
    hbe o2;
    
    cout<<"\n\t\t Regular Employee  \n";
    o1.input();
    o1.display();
    
    cout<<"\n\t\t Hourly Based Employee \n";
    o2.input();
    o2.display();
    
    getch();
    return 0;
}

You class definition needs to include a declaration for each subsequently defined method:

Code:

class re:public person
{
   public:
      void input();
      int empid;
      float basic,da,hra,pf;
};

Also, you need a new IDE!

to MK27: i don't understand why there is a need of writing function declarations in child classes because they are inheriting features of base class-parent.so in my opinion, while inheriting; the function declarations which i wrote in the base class should automatically comes inside sub classes in public section and so they should be visible like char ch[20] is visible.but,then why compiler gives the error :-(

Originally Posted by shikhardeep

i don't understand why there is a need of writing function declarations in child classes because they are inheriting features of base class-parent.so in my opinion, while inheriting; the function declarations which i wrote in the base class should automatically comes inside sub classes in public section and so they should be visible like char ch[20] is visible.but,then why compiler gives the error :-(

If you intend to use the base class version of the member functions, then yes, that is correct: you just use them without re-declaring them in the definition of the derived class. However, if you wish to override, or in this case re-define, certain member functions, then you need to declare those member functions in the definition of the derived class.

Note that I wrote "in this case re-define". All the member functions of person are non-virtual. Therefore, person looks like it is intended to be a concrete class that is not a base class. If it really is supposed to be a polymorphic base class, then at least one of its member functions (or at least the destructor) would be declared virtual. Furthermore, I note that you did not define the person member functions, despite declaring them. Perhaps they should be declared pure virtual instead.

Originally Posted by shikhardeep

to MK27: i don't understand why there is a need of writing function declarations in child classes because they are inheriting features of base class-parent.so in my opinion, while inheriting; the function declarations which i wrote in the base class should automatically comes inside sub classes in public section and so they should be visible like char ch[20] is visible.but,then why compiler gives the error :-(

Yes, the derived classes will inherit the functions. But note the word "inherit."
The derived classed will have the same functions as the base class, not different ones.
When inheriting, you do not inherit function declarations, but the function itself. If you wish to redefine that function to something different, you are going to have to create a new function.

so it means that i have to give all the 3 member functions(input(),calsalary()and display()) definitions separately for re class and hbe class and there is no point of using concept of inheritance as the function definitions are different for both re and hbe classes.The only thing which is therefore common in both the child classes is the char ch[20](used for entry of name of the employee).

Any code savings is worth it.
Besides that, inheritance enables you to use polymorphism.

Originally Posted by shikhardeep

so it means that i have to give all the 3 member functions(input(),calsalary()and display()) definitions separately for re class and hbe class and there is no point of using concept of inheritance as the function definitions are different for both re and hbe classes.The only thing which is therefore common in both the child classes is the char ch[20](used for entry of name of the employee).

No, the interface of the member functions are common, so maybe you should declare them as virtual member functions and override them in the derived classes.

There are two aspects in the use of inheritance. We might use inheritance to inherit implementation, which is what you have in mind. More interestingly, we might use inheritance to implement an interface, thereby taking advantage of supertype/subtype polymorphism at runtime: this way, we can create new derived classes that can be used by existing code that only uses the interface of the base class.