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Programming in Smalltalk

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This chapter shows you how to add new classes of object to your Smalltalk image and how to program their behaviour by adding methods to them. As you do this you will be extending the capabilities of the basic system. For this reason, you should now be saving your image on a regular basis (to avoid losing these changes) and especially when exiting the Dolphin environment.

This is what "programming" is in Smalltalk; producing a new image with the appropriate classes and behaviour to do what you want. A Smalltalk "program" is an image embued with an interacting network of objects. It's a bit like your waking day; when you get out of bed in the morning there is no need to start from scratch again. Instead you are able to pick up exactly where you left off the previous day, with all the objects in your life ready to go. This is what happens when you start a Smalltalk image; everything is there just as it was when you last shut the image down.

Tip: if you are from a more "traditional" programming background you may be confused by this at first and wonder where a Smalltalk program starts. There is no main entry point. When your program loads, the image will already contain the initial set of objects ready to go.

This chapter teaches you how to "program" in Smalltalk.