Difference between a virtual function and a pure virtual function in C++

C++Server Side ProgrammingProgramming

Following table shows the difference between Virtual and Pure Virtual Function:

Virtual Function
Pure Virtual Function
Virtual function has their definition in the class.
Pure virtual function has no definition.
Declaration: virtual funct_name(parameter_list) {. . . . .};
Declaration: virtual funct_name(parameter_list)=0;
It has no concept of derived class.
If a class contains at least one pure virtual function, then it is declared abstract.
If required, the base class can override a virtual function.
In case of pure virtual function derived class has to definitely override the pure virtual function.

virtual function

Example Code

 Live Demo

#include <iostream>
using namespace std;
class B {
   public:
      virtual void s() //virtual function {
         cout<<" In Base 
";       } }; class D: public B {    public:       void s() {          cout<<"In Derived
";       } }; int main(void) {    D d; // An object of class D    B *b= &d;// A pointer of type B* pointing to d    b->s();// prints"D::s() called"    return 0; }

Output

In Derived

pure virtual function

Example Code

 Live Demo

#include<iostream>
using namespace std;
class B {
   public:
      virtual void s() = 0; // Pure Virtual Function
};

class D:public B {
   public:
      void s() {
         cout << " Virtual Function in Derived class
";       } }; int main() {    B *b;    D dobj; // An object of class D    b = &dobj;// A pointer of type B* pointing to dobj    b->s();// prints"D::s() called" }

Output

Virtual Function in Derived class
raja
Updated on 30-Jul-2019 22:30:25

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