System requesters, such as DOS requests to "Insert volume foo in any
drive,"  are created by the system using EasyRequest().  Unless otherwise
specified, these requests appear on the default public screen.

System requests may appear at any time the system requires a resource that
is not available.  The user may be in the middle of an action, the program
may be in any state.

Use the function ModifyIDCMP() to turn off all verify messages before
calling any function that might generate a system requester.  Neglecting
to do so can cause situations where Intuition is waiting for the return of
a message which the application program is unable to receive because its
input is shut off while the requester is up.  If Intuition finds itself in
a deadlock state, the verify function will timeout and be automatically
replied.

 Redirecting System Requesters