4th Dimension 2003 allows you to compile the structure file, the allows you to switch from Interpreted to Compiled mode. The problem is that sometimes, you may want to go back in Interpreted mode. Re-opening the database will still be in compiled mode. How to go back in Interpreted mode?

When launching 4D, select the database that you want to open then, click on the expand button (double arrow on the bottom right of the window) to display more details about the selected database.
You may now select the requested radio button to open the database in compiled mode or interpreted mode.