HP28s: clamshell & pixels?



Can anyone advise me on how the "clamshell" design of the HP28s' has bourne up over the years?

Also, how many pixels are available on the screen? As a newcomer to the site, I was quite surprised to discover that this machine was capable of "worthwhile" graphics - or is it?

Thanks tgroup for recent advice,


I think the clamshell (hinged) design worked fine, and I've not had any problem with that.

I think the pixel count is something like 127 x 32. (Someone will correct me if I'm wrong . . .) It does do something like graphics, but limited in height and resolution. Its major benefit is in providing a multi-line stack display.

I've mentioned before that my son's HP-28S has fallen apart because he carried it in an overstuffed backpack. Apparently, the constant flexing (caused by being pushed into curved shapes by tons of books and paper) broke most of the plastic heat stakes that held the keyboards to the covers. So, the 28s can't stand a lot of flex-abuse.

The worst aspect of the HP-28S design is the battery compartment door. I haven't had the opportunity to use an example of each & every HP model, but this is easily the worst HP battery door I've encountered!

Other than that, the HP-28S is a fine machine, and the unlimited stack RPL interface is, while a bit different, actually very interesting. I loved mine while I was still programming calculators, but have since retreated to the more portable HP-32S for my occasional, everyday use.


I think the display is 161 x 32, 161 columns seems to be a rather unusual value, used also in the HP42S (161 x 16).



sorry to correct you but the display has 137x32 pixels. You can check this by using the LCD-> command. The Stringsize you get there is exact 548 Bytes. Divided by 4 (4 Lines for Characters) you get 137.
As this calculator was new, we created several grafical game programs. Unfortunately ALL are lost because of this rotten battery door :-(

Best regards

Andreas Stockburger

Possibly Related Threads...
Thread Author Replies Views Last Post
  Exotic Clamshell collection Keith Midson 7 715 07-31-2012, 06:57 PM
Last Post: Keith Midson
  Clamshell Battery Contact Repair aj04062 6 607 03-03-2012, 11:21 AM
Last Post: aj04062
  Clamshell Battery Contact Repair aj04062 11 924 02-23-2012, 08:23 PM
Last Post: aj04062
  HP28S screen noise generator Keith Midson 7 656 02-19-2012, 05:35 PM
Last Post: Gilles Carpentier
  HP28S battery door trouble David Griffith 23 1,667 02-08-2012, 08:24 AM
Last Post: Neil Hamilton (Ottawa)
  HP-28S/Clamshell Keyboard Test aj04062 2 368 08-03-2011, 09:02 PM
Last Post: aj04062
  Another approach - shucking the clamshell, further. Book? Wanderley Navarro 8 881 06-07-2011, 07:23 AM
Last Post: Randy
  HP 28S: shucking the clamshell, further. Book? Geoff Quickfall 8 695 06-03-2011, 03:42 PM
Last Post: Geoff Quickfall
  Clamshell, shucking the clamshell, any thoughts! Geoff Quickfall 13 991 05-31-2011, 11:01 PM
Last Post: Keith Midson
  HP28S - made in Indonesia? Keith Midson 1 267 11-01-2010, 08:06 AM
Last Post: Jeff O.

Forum Jump: