what is abstract class in c 2b 2b

1//Code by Soumyadeep Ghosh 
2//insta : @soumyadepp
3//linked in : https://www.linkedin.com/in/soumyadeep-ghosh-90a1951b6/
4#include <bits/stdc++.h>
5
6using namespace std;
7
8class person
9{
10  string p_id;
11  public:
12  virtual void get_info()=0; //declaring person as abstract class
13  virtual void show()=0;
14};
15
16class student:public person
17{
18  string name;
19  int roll_no;
20  public:
21  /*overriding the pure virtual function declared in base class otherwise
22    this class will become an abstract one and then objects cannot be created
23    for the same*/
24    void get_info()
25    {
26      cout<<"Enter name of the student "<<endl;
27      cin>>name;
28      cout<<"Enter roll number of the student "<<endl;
29      cin>>roll_no;
30    }
31   void show()
32   {
33     cout<<"Name : "<<name<<" Roll number: "<<roll_no<<endl;
34   }
35};
36
37int main()
38{
39  person *p;
40  p=new student;
41  p->get_info();
42  p->show();
43  return 0;
44}
45

1struct Abstract {
2    virtual void f() = 0; // pure virtual
3}; // "Abstract" is abstract
4 
5struct Concrete : Abstract {
6    void f() override {} // non-pure virtual
7    virtual void g();     // non-pure virtual
8}; // "Concrete" is non-abstract
9 
10struct Abstract2 : Concrete {
11    void g() override = 0; // pure virtual overrider
12}; // "Abstract2" is abstract
13 
14int main()
15{
16    // Abstract a; // Error: abstract class
17    Concrete b; // OK
18    Abstract& a = b; // OK to reference abstract base
19    a.f(); // virtual dispatch to Concrete::f()
20    // Abstract2 a2; // Error: abstract class (final overrider of g() is pure)
21}

1struct Abstract
2{
3     virtual ~Abstract() = 0;
4};
5
6Abstract::~Abstract() {}
7
8struct Valid: public Abstract
9{
10        // Notice you don't need to actually overide the base
11        // classes pure virtual method as it has a default
12};
13
14
15int main()
16{
17    // Abstract        a;  // This line fails to compile as Abstract is abstract
18    Valid           v;  // This compiles fine.
19}