HP-41 program checksum


Hi, does anyone know how to recall the Checksum
of an HP-41 program in Extended memory? ( perhaps synthetic instructions? )
Best regards,


Hi JeanMarc,

The checksum is stored as the first byte after the END. Locating it is somewhat difficult, yet EMDIR gives important data. Remember that there are two registers (overhead) used for filename and pointers.

Recall of the data is another problem. One would suppose that lowering the curtain then using RCL 00 would suffice, unfortunately the RCL function normalizes (distroys) the data. The only HP module that I know of that can do a non-normalized recall is the HP-IL Development module (RG-BUFX function with lowered curtain).

Best regards,


Hi Doug,
thank you for these informations.
Best regards.

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP-41(CL): The easiest way to transfer FOCAL programs from a Linux PC to the HP-41 Geir Isene 13 2,742 12-05-2013, 02:40 AM
Last Post: Hans Brueggemann
  HP Prime: run a program in another program Davi Ribeiro de Oliveira 6 1,219 11-11-2013, 08:28 PM
Last Post: Davi Ribeiro de Oliveira
  Updated PPC DVD Version 2.10: HP-41 Searchable Program Files and Scannable Barcode Jake Schwartz 3 919 09-27-2013, 09:51 PM
Last Post: Olivier (Wa)
  Looking for PLTMX80 program for HP- 41 Ángel Martin 1 455 10-19-2012, 05:21 AM
Last Post: Ángel Martin
  New 41 model to use rom of "big" program Olivier De Smet 4 817 10-03-2012, 07:35 PM
Last Post: Brian Walsh
  Editable PDF Docs for HP-41 Program Documentation? Namir 8 1,239 03-08-2012, 11:13 PM
Last Post: John Robinson
  HP-41 Ohms Law Program Jeff Davis 45 4,720 12-28-2010, 09:23 PM
Last Post: Ren
  HP-41: Sail boat parameter program Geir Isene 0 378 11-24-2010, 01:37 PM
Last Post: Geir Isene
  HP-28C ROM checksum addresses? Christoph Giesselink 0 357 07-25-2010, 08:25 PM
Last Post: Christoph Giesselink
  HP 35s checksum repeatability observed JJB299 0 364 06-15-2009, 10:06 AM
Last Post: JJB299

Forum Jump: