(Comp.sys.handhelds)
Item: 3629 by ftg0673 at tamsun.TAMU.EDU
Author: [Rick Grevelle]
  Subj: HP48 CRASH Library (Taking Control)
  Date: Thu Jul 04 1991

This is an abbreviated version of my CRASH library.  With the availability of
RAM cards, it soon became apparent that libraries were superior to the
directory structures to which we had become accustomed in the HP28S.  Many of
the 48's features are more easily exploited via the use of RAM cards, and it's
only a matter of time before it's discovered how to completely assume control
of this machine.

While currently there isn't adequate time to fully explain how the library
accomplishes all that it does, perhaps it will suffice to exemplify a few of
the more important techniques for those who already have some knowledge of the
48's operating system.  Therefore it's being posted without detail for only the
fundamentals will be addressed here.

Numbered 1012, the library is actually unnamed.  Its original purpose wasn't as
its name implies, but rather was to restore the calculator exactly as it had
been before a crash.  This was made possible for one main reason; I own RAM
cards from which all of my programs are used.  It became necessary for me to
utilize directory structures such as those HP uses in ROM for various menus
which contain the user language commands, functions, and operations.

This abbreviated version of library 1012 references two other libraries, of
which neither is necessary.  The libraries, MLDL, and HACKIT, are used for
illustration only, and were intended to embellish the directory structure I am
hoping to illustrate.  It is therefore advisable to install both of the
libraries in order to realize the full benefit.

First, before installing 1012, it would be a good idea to archive anything that
is currently being stored in the intrinsic RAM.  Don't despair, as the library
is safe, but it could make some rather startling modifications one might not
expect.  Unfortunately, for those users who haven't yet purchased a 128K or 32K
RAM card, there is not much precaution that can be taken :-(.

After installation the CST variable should be present in HOME.  This is the
only part of static RAM I use, and surprisingly, this powerful little custom
menu is only 117 bytes.  Now press the [CST] key; the three directories are
completely unlike user directories, and virtually identical to the ones used in
ROM by HP.

Options available here are numerous and widely varied.  It's possible to run
programs in the background with these structures with only minor changes in the
main directory.  Furthermore, unlike user directories, nesting will save
memory, shrink the size of the CST list, and will not slow the accessing of
variables.  This is because even though directories appear to be nested, it's
not the case at all; they are actually flat as are libraries.

If this sounds too outrageous to be true, be assured it's quite true.  Let's
see how it's done using the flag browser Wickes posted to this group only a few
months ago.  The third directory that appears on the menu page when [CST] is
pressed is entitled UTILS.  Before pressing UTILS, perform a [orange shift] [-]
key sequence to begin a user program in the command line.  Now pressing UTILS
will result in a change to that directory.  Now press all six keys on this
page; note that PEEK, and SEEK are the only two commands on this page that I
have made programmable.

Implementing the [NXT] key will reveal the next page, and two more apparently
nested directories.  The directory labeled FLGS is the flags browser Wickes
posted, and it is this program that we are going to run without affecting the
program being built in the command line that should look like this: 

<< PEEK SEEK >> 


Note the cursor flashing just after SEEK; now impliment the flag browser by
pressing FLGS.  Amazingly enough, both routines are apparently running.  You
are free to utilize any of the commands within the flag browser (see Wickes'
posting for details).  When you are finished playing around in the browser,
simply press [ON] to exit the browser and return to the command line.  If at
any point you pressed [ENTER] while in the browser, you'll notice that the
tagged object that command generates has been pushed to the stack instead of
appearing in the command line.

Certainly I do wish time was allowing for a more detailed explanation of all
this.  Currently, Robert Ellis has devised an elaborate directory/menu scheme
which I'm hoping he will post soon that further expands upon these technics,
but remains remarkably user friendly.  What I've done in library 1012 is not
overly complex, just detailed; so it shouldn't be too difficult to take apart
and digest.


Rick Grevelle
(409) 774-1169
ftg0673@tamsun.tamu.edu