Analog Devices VisualDSP++ 3.5 Manual page 166

Memory Map Pane
Figure 4-25. Insert Gap Dialog Box
You may insert a gap at the start of the memory segment or the end of it.
If the start is chosen, the Start address for the gap is grayed out and you
must enter an end address or size (of the gap). If the end is chosen, the
End address of the gap is grayed out and you must enter a start address or
size.
4-32 VisualDSP++ 3.5 Linker and Utilities Manual
for 16-Bit Processors