An object consists mainly of parameters and scripts.
Parameters are the things the user can set. You see the parameter list in the object settings. You edit the parameters to make the object do what you want. Examples of parameters: length, material, quantity, style, spacing, pen, slope, fill...
There are twelve types of parameters. When you create a parameter, you select a type depending on what it will do. The types are: Length, angle, real number (can have decimals), integer (whole number), boolean (a yes/no, on/off, 1/0 switch), text (can include numbers), material, linetype, fill, pen (attributes), separator, and title. The last two help organize the parameter list and don't affect the object itself.
The parameters appear to user in different forms depending on their type. Attribute parameters (pen, etc.) offer the user a typical flyout palette for that attribute.
Scripts do the actual work of creating the object, and are invisible to the user. Different scripts are read depending on the object and the situation.
The 2D script draws the 2D symbol for the floor plan.
The 3D script builds the model of the object.
The 2D and 3D scripts each have their own shape statements, and they are separate. All the 2D commands have a "2" in the name.
The master script is a depository for code that might be used by more than one script. It is executed before anything else, when any script is executed. Most developers use the master script for housekeeping and laying down the rules.
The parameter script modifies and enhances the parameter list. This is where you can put a list of options (values) for a parameter. You can also hide and lock parameters, depending on the situation. This is a ways over in the book.
The interface script creates a custom graphical interface as an alternative to the parameter list. Out of the scope of our discussion.
The property script is also well out of scope.
The work of editing objects consists of creating parameters and editing scripts. You do this work in the object editing environment. These are the windows you see when you Open Object. The library part editor window contains the parameters, and this is where they are created. It is also the home base of the object, where you can open any of the other windows. Each script can have its own window, or you can choose to display the scripts one at a time in the master window. I always open scripts in their own windows.
For a description of the controls in the library part editor window see the Archicad Reference Guide, search for 'GDL Object Editor'.
In addition to the main window and the script windows, there are windows for the 2D symbol and the preview picture. The 2D symbol will be drawn if the 2D script is empty, or if it contains fatal errors. The preview picture is an optional (technically, but use it) icon for display in the object settings.