Q: How can I get information on programming the internals of the HP?

A: The HP Palmtop Developer's Guide is being distributed by Thaddeus Computing (see ad, page 35). Price is $79.00 US, plus $5.00 shipping inside US, $12.00 shipping outside US. It contains full documentation on the internals of the HP Palmtops, plus software for developing system-manager compliant applications. You'll need to supply your own compiler and/or assembler (MSC 6.00AX and/or MASM 5.1 are recommended). Order from Thaddeus Computing, 57 E. Broadway, Fairfield, IA 52556 (800) 809-5603, (515) 472-1875, 75300.2443@compuserve.com

For those who don't want to purchase the full developers kit, there is a library called PAL <See Shareware/Freeware index> (Palmtop Application Library) which is a collection of C language functions that provide DOS programs with the look & feel of HP 100/200LX built-in applications. It provides graphics functions, support for windows, menus, dialog boxes, etc. It is free, and available on the HPHAND Forum on CompuServe, as well as ftp .monash.edu.au, eddie.mit.edu, and butler.sidewinder.com.

Many of the HP's interrupts are documented in the interrupt list, maintained by Ralf Brown, available at ftp://oak.oakland .edu/simtel/msdos/info/inter48x.zip (there are four files, replace the x in the address above with an a, b, c or d).

Of course, if you only want to program the HP as a DOS machine, without accessing any of the Palmtop's unique features, there are plenty of widely available books on DOS programming.

If you need the file formats for the built-in applications, GDBIO <See Shareware/Freeware index> (on eddie) has C source code which should be a good starting point.