why we don't make pointer of child/derived class which points to base class ?

[Rayan jutt]

why we don't make pointer of child/derived class which points/assigns to base class object?
for example:

parent a; // a is a parent class object!
child * p = & a; // p is child class pointer !

why we do not do this in c++ ?

[keskiverto]

Parent is not a child. It does not have the interface of a child.

A question for you. What will "s" contain:

T a;
T * p = &a;
T * s = p+1;

[Rayan jutt]

if we print value of p it will print 00cofefc on console
if we print value of s it will print 00coff00 on console !

[keskiverto]

Yes, but what does that mean? Btw, what was the T in your test?

[Rayan jutt]

I am not very much familiar with hex numbers so i am not sure what that does mean !
you may explain this to me !

T is a class name/user defined data type (parent class) !

[keskiverto]

Repeat with these then:

class A {
  int a;
};

class B : public A {
  int b;
}