A user of REC/C will deal mostly with two windows, the main window and the auxiliary display window. There may be other panels and windows; for example the program menu makes its presence known every time the program is executed, and is so ubiquitous that it may not be even be counted amongst the program's windows. The main window of the Interface Builder, which customarily sits in the lower left hand corner of the screen as the interfaces are built, exhibits all the panels, windows, and accessible Objects, as shown for REC/C in Figure 2.
The main window, labelled ``execute'' in Figure 2, comes with two alternative forms, one of which was shown in Figure 4. The difference between them is that the browser panel can be exchanged for a text panel, into which programs can be read from disk storage, or composed on the spot. Traffic goes both ways, because the contents of the window can be transferred to the disk, either as a new file or as a correction to the existing file. The text handling variant is shown if Figure 3. The button at the bottom of the panel, displaying either the title ``use external source,'' to load the text insert, or ``load internal source'' to load the browser insert, governs the transition between the two forms.