modsim3

I. What is Object Oriented Programming?

1.1 Examples:

C++: General purpose.

Java: Internet.

MODSIM III: Discrete event simulation.

1.2 Procedural programming vs. Object oriented programming:

MODSIM III

job=reportposition;
car54position=task(car54,job);
                            /|\
                        action
task(car54,job)
{
   if(job.eq.reportposition)
       x=position(car54);
   else
       x= ...;
   return x;
}

ASK Car54 TO ReportPosition
             /|\                     /|\
        object             method
                                     /|\
                       one of several methods

Note: object includes methods (functions) and fields (data).

In this case field of object is hidden, it is the
value returned by method.

Procedural programming:

Action oriented: Groups of actions => functions => programs.
The unit of programming: function.
Data plays secondary role (in support of actions).

Object oriented programming:

Object oriented: Real world objects and behavior

=> software objects (fields + methods)

=> abstract classes (data + functions)

The unit of programming: object.
Data is part of the object.

1.3. More examples :

MODSIM III statement:	Explanation:
ASK Vehicle TO Stop ASK Aircraft TO Stop ASK Bike TO Stop ASK Boat TO Stop /\|\ /\|\ object method	Object's stop method sets speed field value to 0. Different objects can be given same generic method, but different behavior
CarSpeed := ASK Vehicle speed /\|\ /\|\ /\|\ field of object1 object2 field	Field value of another object can be obtained through statement

1.4. Characteristics:

Object oriented: Object as the basic unit. It includes data and functions which are tied together. Objects can communicate with each other but implementation info is hidden. Polymorphism.

Class relationship: Objects of same class (or type) have same characteristics.

Inheritance: New classes of objects can be derived by inheriting characters of exiting classes, while having their own characters.

Messages and behaviors: An operation is described in terms of a message sent to object, which decides what to do with the message.

1.5. Questions:

What is the characteristics of object oriented language?
What is the object, method and field in the following MODSIM III statements?

TELL truck TO ProceedTo(NUS);

ASK ranGen TO SetSeed(randSeed);

ASK Singaporeair20 position;

OBJECT Rocket; TELL METHOD launch(speed, orientation);