This is the area for editing multiple source files, each in its own tab. Select which source file to edit by clicking on its tab, or close a tab by clicking on the tab's close (X) icon.
Open a file through the File menu, the Toolbar, or by selecting a file in the Project File List (see IDE Layout - Project File List).
An editor may also be opened automatically if:
In these cases, the editor will open to the line that is active or that caused the error.