Design time environment variables help govern the behavior of Forms Builder. These environment variables must be set on the machine where Oracle Developer Suite is installed. For example, on Windows platforms you set them in the Windows Registry.
Java class files: Forms Builder needs access to certain Java classes for some of its features, such as Help, the debugger, and the Java importer. You set FORMS90_BUILDER_CLASSPATH so that Forms Builder can find the Java classes it needs during development and testing of an application.
Icon files: Forms Builder enables you to create buttons with iconic images. You can use .ico, .gif, or .jpg images. You set UI_ICON to the directory path where these images are located. You set the environment variable UI_ICON_EXTENSION to tell Forms Builder which type of image to display on buttons. Valid values are ico (the default), gif, or jpg.
Although you can use .ico images to display on iconic buttons within Forms Builder, such images will not be displayed when running the form — use .gif or .jpg files for deployed icons.