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Discussion 4 - Robert Simpson
Sketchpad is a very early visual editor that incorporated colored pixels and an object oriented design. It was developted by Ivan Sutherland from MIT and incorporated such things as inheritence and polymorphism. By creating a master sketch you could then extend that to other instances of that sketch. Then, by simply changing the master, all of the child sketches would update as well.
- What is Sketchpad?
Simula was a general purpose procedural language that incorporated the same object oriented principles from Sketchpad. In Simula the programmer would create processes which hold data and control who has access to it. This was the first demonstration of encapsulation in programming. This programming language got its name because it was developed around the thought of creating simulations.
- What is Simula?
These languages started the movement of object oriented programming. Alan Kay was inspired by how these unique principles were being used in each language and wanted to create a language which incorporated the best parts of both ideas. This is when Smalltalk was made. Squeak came along later on when Alan Kay, Dan Ingalls and Ted Kaehler all started working for Apple and wanted to create a more sophisticated version of smalltalk. The principles of both a visual interface from Sketchpad and the object oriented design of both languages combined created what we now know as Squeak.
- What do they have to do with Squeak?
The idea of the personal computer pushed this type of programming and development. Early development on computers for children gave programmers a goal to keep their software simple for easy understanding. As technology became more accessable to middle class America a lot of software development started happening. These principles of programming were still the most useful.
- How did OO ideas get out into the mainstream (out of the research lab)?
Java and Squeak are both object oriented programming languages. They both run on a virtual machine and can both be coded entirely by text. However, in Squeak there is a whole visual interface that java lacks. You never have to make any frames or windows because everything sits inside Squeak's own bounds. You are also forced to write all of Squeak's code inside the virtual machine itself. In Java the virtual machine is not launched until the program is compiled and executed.
- How are Java and Squeak similar and how are they different?
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- Robert Simpson last edited on 10 December 2005 at 3:41 pm by c-69-180-9-249.hsd1.ga.comcast.net
- Fall 2005 Discussion 4 last edited on 6 December 2005 at 3:45 pm by r36h51.res.gatech.edu