Search the Openlist for the device named in Devnam.
If not found, trap execution.
Otherwise, perform the following
operations:
Set $IO to the device named in
Devnam, and make this device the current device for all input and
output.
If Result contains any device parameters, find the
device named in Devnam in the Devicelist, and change those
parameters which appear in Result to their new value from
Result.
Perform any initialization procedures for the device named in
Devnam according to its device parameters in Devicelist.
Devnam.