A temporary control self-destructs when its home location is overwritten by another control or by textual output. Temporary controls can also be destroyed in the same manner as permanent controls. A temporary control self-destructs in the following circumstances:
The runtime system maintains location information to the nearest 100th of a character cell. If the newly created control is placed in the same row and column as a temporary control (or less than one one-hundredth of a cell away), it destroys the temporary control. Note that moving a control on top of a temporary control does not destroy the control (the runtime system assumes that the temporary control is about to be moved, also. This occasionally happens with Screen Section updates when several items are of variable size). Only a newly created control can destroy a temporary control.
The temporary style is applied when a control is first created and does not change during the life of the control. If you attempt to apply both the PERMANENT and TEMPORARY style to a control, the PERMANENT style is used.
A control can also be made temporary using the TEMPORARY_CONTROLS runtime configuration variable.