Coo, I never knew that MS-DOS had STDAUX and STDPRN, I only knew about PRN (I think it mapped to LPT1).
Don’t you love the old new thing :)
The standard MS-DOS file handles are as follows:
handle name meaning 0 stdin standard input 1 stdout standard output 2 stderr standard error 3 stdaux standard auxiliary (serial port) 4 stdprn standard printer
–jeroen
via: The importance of error code backwards compatibility – The Old New Thing – Site Home – MSDN Blogs.