It is a classic Global Mapping exercise presenting ^SPOOL as Class / Table
Device #2 named SPOOL dates back to the predecessors of Caché and IRIS
It was the first "%Stream" like option to buffer output before printing.
It is also the first and till today the most simple way of output redirection.
This is also an example of a mapped Global.
USE 2 redirects the output into the Global ^SPOOL