Hi,
Why an abstract class can't be instantiated? Want to know the exact reason for this.
Thanks & Regards,
Anisur

Give us an example of what you mean. Whar exactly are you trying to do?

Alan

Alan, I think this is plain english....poor chap just wanna know what goes behind the scene so that we cannot instantiate an abstract class......

because it is a class that is specifically designed to be only derived from.that class has pure virtual functions that must be overriden by the class inherits abstract class.instantiating a class that has pure virtual functions is pointless and might cause compiler errors i guess.for example think of a Bird abstract class that has many pure virtual functions like fly() that have to be defined by the inherting bird kind lets say Sparrow.If you could instantinate Bird class lets say Bird mybird then mybird::fly() and fly function is undefined that would not be logical.besides can you show me a bird that is only a bird? no you can not do that.so instantiating a bird class is not logical.i am not an expert but these are the reasons i can think of.

But even when the abstract class provides definitions for each of its
pure virtual functions, the class still cannot be directly
instantiated. There really is no compelling technical reason why
abstract classes could not be instantiated; after the language rules
could simply be adjusted and have the compiler provide an empty
definition for a pure virtual function - in much the same way that the
compiler provides a default constructor when needed. Instead, the
prohibition against instantiating an abstract class is a deliberate
feature of the language. An abstract class cannot be instantiated
because the definition of an abstract class is one that cannot be
instantiated.

In C++, abstract classes help keep separate class interface from
implementation. An abstract class need specify only an interface.
Because it cannot be instantiated, it has no need no provide any
implementation of its own. Instead the pure virtual mechanism forces
subclasses to provide part or all of the implementation. By keeping the
two separate, the resulting code is more portable, has few dependencies
and is overall "cleaner" than one in which the interface and
implementation are tightly intertwined.

You can create pointer or reference to abstract class but not object.

Linux is the best OS in the world.

you may be able to create a pointer to abstract class to use polymorphism but you can not create reference to abstract class because it is not an object..and you can not reference something that is not a variable or object as far as i know..correct me if i am wrong.