Submitted by Steve Fewell
Set A to #&02 --> this is the OSARGS (&FFDA) option to obtain the file's EXT value.
Call &AACB (in the =PTR routine) to read the '#' character (issuing 'Missing #' error if not found), read the Integer
after the '#' (the file channel number) - store the LSB of this value in Y, Call OSARGS (with X [the parameter block] set to
the IWA (#&2A), and exit with A = #&40 (as the result value is an Integer).
After the call to OSARGS (&FFDA), the IWA will contain the EXT value for the file that is opened on channel Y.
|AAC5||169 002||A9 02||LDA#&02|
|AAC7||128 002||80 02||BRA 2 --> &AACB Get '#', get channel number (in Y) & call OSARGS to return the EXT value in the IWA|