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From: ji@close.cs.columbia.edu (John Ioannidis)
Newsgroups: comp.sys.handhelds
Subject: User-defined libraries: how?
Message-ID: <6757@columbia.edu>
Date: 13 Mar 90 19:45:56 GMT
Sender: news@columbia.edu
Reply-To: ji@close.cs.columbia.edu (John Ioannidis)
Organization: Columbia University Department of Computer Science
Lines: 32

I'm quoting from the hp-48sx manual, page 651:

	A _library_ is an objet that contains named objects that can act as
	an extension to the built-in command set. you cannot view or change
	the contents of a library. Libraries can exist in application cards,
	or they may be copied into RAM. Howeve, libaries cannot be created by
	the HP48. 
	
Like any self-respecting HP-calculator-old-timer, I take that "cannot
be created" as a challenge. My understanding is that the there is no
*physical* difference between the port ram or rom and the built-in ram
and rom; the address space appears to be linear, and there is probably
some table that defines what part of the memory is rom, what is
"independent" (or whatever they call it) ram and what is user ram.
(in the 41 they were completely disjoint address spaces and they were
accessed using completely different machine instructions). 

My guess is that it should be possible to create an object in ram, then
fiddle with its attributes using the "front panel" hex editor and have
the machine think it's a "library" (since, after all, libraries can be
copied in ram. This could even be a way of getting around the various
bugs in the early releases of the firmware.

Is anyone workign along those lines? Will information like this be
available in the "programmer's reference manual"? 

Speaking of which, can anyone from HP tell us what is expected to be
there? I don't want a hand-holding tutorial on user-level programming,
I want details of how to access low-level features effeciently (like
scrolling regions of the display, defining my own fonts and commands, etc). 

/ji