It is relating to computer coding, I don't understand it yet, but I've found some reference material for you. http://www.faqs.org/docs/think_java/TIJ303.htm http://en.wikipedia.org/wiki/Alan_Kay --------- Alan Curtis Kay (born May 17, 1940) is an American computer scientist, known for his early pioneering work on object-oriented programming (OOP). The paragraph that you quoted is one of the characteristics of OOP according to him. Alan Kay summarized five basic characteristics of Smalltalk, the first successful object-oriented language and one of the languages upon which Java is based. These characteristics represent a pure approach to object-oriented programming: Feedback Everything is an object. Think of an object as a fancy variable; it stores data, but you can “make requests” to that object, asking it to perform operations on itself. In theory, you can take any conceptual component in the problem you’re trying to solve (dogs, buildings, services, etc.) and represent it as an object in your program. Feedback A program is a bunch of objects telling each other what to do by sending messages. To make a request of an object, you “send a message” to that object. More concretely, you can think of a message as a request to call a method that belongs to a particular object. Feedback Each object has its own memory made up of other objects. Put another way, you create a new kind of object by making a package containing existing objects. Thus, you can build complexity into a program while hiding it behind the simplicity of objects. Feedback Every object has a type. Using the parlance, each object is an instance of a class, in which “class” is synonymous with “type.” The most important distinguishing characteristic of a class is “What messages can you send to it?” Feedback All objects of a particular type can receive the same messages. This is actually a loaded statement, as you will see later. Because an object of type “circle” is also an object of type “shape,” a circle is guaranteed to accept shape messages. This means you can write code that talks to shapes and automatically handle anything that fits the description of a shape. This substitutability is one of the powerful concepts in OOP. Feedback

how to understand this words "while hiding it behind " sorry my english is poor

Students will not be intimidated by this project. It sounds simple. Yet the project will make students think. They must think about what to package and how. This is an important part of advertising. Students will gain a lot of creative experience with it, yet it is not going to cause them stress. Packaging feels very familiar to students because it is everywhere.

For instance, in Java, in your main class you can create an object called maze1 from class Maze: Maze maze1 = new Maze(10, 10); And then in your class Maze you can have an attribute called mymaze which is made of objects from class Wall: private Wall mymaze[][]; Then you can create objects mymaze[1][2] and mymaze[1][1] which are objects from class Wall inside your object maze1. mymaze[1][2] = new Wall(); mymaze[1][1] = new Wall(); So, when you write "new Maze(10, 10)", depending in how you implemented the Maze class, the whole Maze gets made of Wall objects, so you hide the complexity (mymaze[i][j]= new Wall() for i and j from 1 to 10) behind the simplicity of "new Maze(10,10)". I think this is the idea. Sorry Java programmers for any mistakes.

When you drive a car, you only care about how to steer. Are you thinking about how those gears excactly work? that is the object which engineers have made it simple. I wrote the words down and just a give a simply click on the button then I have answer the question. but there are hundreds of lines of code behind the click event. Got it?