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Q) What is “message passing” what is the purpose of message passing?




A)
->in an object oriented system objects communicate one another through message passing.
->in implementation of message passing the fallowing things are involved

1)      message sender (object)
2)      message receiver (object)
3)      message (method)
->Calling method belongs to which object that object is the message sender. Called method belongs to the object. That object is the message receiver.
->One object calling a method from another object is nothing but the first object is sending a message to the second object.

Ex:
class A
{
       void x()
       {
              B b=new B();
              b.y();//message passing
       }
}
class B
{
       void y()
       {
             
       }
}

->in the above example, object of class A is the message sender and the object of class B is the message receiver. Method call y is nothing but message passing.
->whenever one object needs the service of another object it communicates with that object using message passing.
->message sender object is service request object and message receiver object is the service provider object.

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