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Discussion 4 - Priyanka Mahalanabis

From Midterm Review Summer 2003:

History of Object Systems

1. What is Sketchpad?

Sketchpad is graphical editor created by Ivan Sutherland at MIT in 1963. It was the first object-oriented graphics editor. One could create an object that could be manipulated as distinct from other objects. It allowed a person to define a 'master drawing' and then define a set of 'instance drawings' where each instance was like its master. If the master was changed, all instances would reflect that change.

2. What is Simula?

This is a programming language that was defined to make simulations easier to implement. Created in Norway in the 1960's, it allowed user to define an activity from which any working versions of that, named processes, could be created - like the master/instance drawings of Sketchpad. Each process was a different object from another and each simulation had its own class. Simula also implemented the concept of encapsulation.

3. What do they have to do with Squeak?

Since Squeak was written in Smalltalk, Smalltalk was influenced greatly be Sketchpad and Simula. Kay's FLEX machine (personal computer) was intended to serve the needs of an indivdual. He described it as a "meta-medium" - that which would encompass text, sound, graphics, etc. To build this he implemented many of the ideas of Sketchpad (to draw) and Simula (to simulate the real world.)

4. How did OO ideas get out into the mainstream (out of the research lab)?
Though the object oriented principles began with Simula it was not until the 1980's with languages such as C++ and ADA that object-oriented design and analysis actually became mainstream.

reference: History of Object Systems

5. How are Java and Squeak similar and how are they different?

Java and Smalltalk are similar in that they both have garbage collection and they are both compiled. They also both handle only single inheritance. They are different in that Java is statically typed and Smalltalk is dynamically typed. While the two languages are similar in that they are object-oriented, Smalltalk is considered pure object-oriented whereas Java is not.

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