The development environment is a tool designed to create, launch, and test user forms, units, and assemblies.
To start the Development environment window, select the Tools > Development Environment item, or create an Assembly/Unit/Form/.Net Assembly in the object navigator.
If you select the Create > Form menu item, the development environment window shows an empty form without components:
The dialog box for creating a unit (module) looks the same, but no form is available. Saving a form/module for the first time shows a dialog box where you can specify a folder to save the form/module to. When you create an assembly (.NET assembly), it is saved to the repository object from which the Create command was executed.