🚀 go-pugleaf

Ok folks, does anyone know what really happens when you hit ctrl-printscreen?
I know that stdout is echoed to stdprn, but how does this come about?  Stdprn
(file handle 5) is opened for write, and gets a copy of every character
written to stdout (file handle 1).  At what point does this duplication occur;
what control bits are changed?  In short, how can you tell at a glance
(without peeking at the keyboard buffer) that ctrl-prtsc has been pressed at
some point in the indeterminate past?  I understand the theory of file
handles, but none of my references mentions how file handles are mapped to
devices or disk files, where you might find information on open files, or in
general how DOS uses file handles internally.

In a similar vein, why are stdout and stdprn the only files that have this
output-echoing capabililty; why can't I echo stdout to a disk file (without a
printer redirector)?  4DOS has a 'Y' command to do this; are they just
kludging around a DOS limitation, or am I missing something?

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Paul Selkirk                                                   paul@ftp.com 
FTP Software                           26 Princess St., Wakefield, MA 01880