c++ abstract class keyword code example

Example 1: what is abstract class in c++

//Code by Soumyadeep Ghosh 
//insta : @soumyadepp
//linked in : https://www.linkedin.com/in/soumyadeep-ghosh-90a1951b6/
#include <bits/stdc++.h>

using namespace std;

class person
{
  string p_id;
  public:
  virtual void get_info()=0; //declaring person as abstract class
  virtual void show()=0;
};

class student:public person
{
  string name;
  int roll_no;
  public:
  /*overriding the pure virtual function declared in base class otherwise
    this class will become an abstract one and then objects cannot be created
    for the same*/
    void get_info()
    {
      cout<<"Enter name of the student "<<endl;
      cin>>name;
      cout<<"Enter roll number of the student "<<endl;
      cin>>roll_no;
    }
   void show()
   {
     cout<<"Name : "<<name<<" Roll number: "<<roll_no<<endl;
   }
};

int main()
{
  person *p;
  p=new student;
  p->get_info();
  p->show();
  return 0;
}

Example 2: cpp make class abstract

struct Abstract
{
     virtual ~Abstract() = 0;
};

Abstract::~Abstract() {}

struct Valid: public Abstract
{
        // Notice you don't need to actually overide the base
        // classes pure virtual method as it has a default
};


int main()
{
    // Abstract        a;  // This line fails to compile as Abstract is abstract
    Valid           v;  // This compiles fine.
}