Arity
The arity (number of arguments) of your DDF. In APS 3.0, the maximum allowed value is 4, and the minimum is obviously 1. After writing the arity, the function header appears in the gray box above the code window.

Definition
Use this box to write a brief description of the DDF for your future reference. The text you write here will appear in the Definition column on the Functions Panel.

DDF Code Window
You design or edit the code of your own functions (DDFs) in the code window. The code must be in Java Script and can be tested for syntax errors before including it in the function set.

Test
Tests the syntax of the Java Script code of your DDF. The results of the test are written in the gray window below the code window.

Stop
Allows you to stop the testing process.

Save
Saves the DDF and includes it in your function set with the default weight of 1.

Cancel
Closes the Edit DDF window without saving the modifications made there.