Sometimes you may need to use an external program to edit a file in the workbench. This can occur, for example, where the workbench has no editor for that file type.
The external program will be used if that program is registered as the system default editor for that file type, and no other editor is registered for that file type in the workbench. For example, the default editor for HTML files is an HTML browser that launches outside the workbench window. If you open an HTML file from the workbench, the file will open (outside of the workbench) in the system's default HTML browser.