The word Virtual

Question

What do the actual word Virtual mean in programming like a virtual function? When someone saids send a virtual message? What does virtual mean?

Vulpes · Answer

In the context of an object oriented programming language a virtual method of a class is one where the runtime type of the object on which it is invoked determines which version of the virtual method is called at runtime. So if you have a class Parent which declares a virtual void method called MyMethod and this method is overridden in a derived class Child then: Parent p = new Parent(); p.MyMethod(); // calls Parent's version Child c = new Child(); c.MyMethod(); // calls Child's version Parent q = c; q.MyMethod(); // calls Child's version because the runtime type of q is Child not Parent In other IT contexts something is said to be 'virtual' if : 1. It has the same effect as what it's applied to but is actually something different; or 2. Isn't real but is simulated to appear real to the user. Examples include virtual memory and virtual reality. I don't think that 'virtual message' is a standard IT term but it does seem to be used in some commercial contexts. See for example: http://www.virtualmessage.co.za/