Seeking 42S Inspiration


If someone here can come up with the right idea, I'll be really grateful!

Situation is that I've had a 42S for a couple of months now and the only programs I've written have been noddy programs to check I understand how it works.

But now I've really got the urge to write a proper program and ideally, I want to write a game. Problem is, I can't think of anything suitable! I don't want to re-hash all the old ideas or regular candidates for calculator games. I want something that will be worth playing and fun. It will have to be turn based of course (unless there is a secret way of scanning the keyboard without halting program flow) and with nearly 7K available and limited graphics, there has to be something good out there.

Anyone able to come up with a cracking idea please?

Put your thinking-caps on please Ladies and Gentlemen!

Sincere thanks in advance for any suggestions :)



A full blown gladiator game where you build a character, win money, buy new weapons and armor, and where the real game is in the close combat tactics of attack/parry combinations.

I've been wanting to make such a game for the HP-41. If you start, I will pitch in :-)


Thanks for the idea Geir. I am having trouble seeing how this type of game would work in a turn-based setup. I've seen games that are similar to what you describe but they have been realtime, arcade type games. Is there a well known existing game that does what you are suggesting that I can look up and examine? Thanks :)



Methinks Geir spoke with tongue in cheek.


Nope, I was dead serious. And with the advent of the NoV-64 & ICEBOX.ROM, we have an enormous amount of memory available to accomplish stuff that you needed a C64 to do in the ole' days :-)


A turn based gladiator game could be as good as a real time time one IMO.

Remember the good old Dungeons & Dragons Role-Playing game?
Or with a better combat system, we have the
Amar RPG . Be inspired :-)

I once played an around-the-table Role-Playing game called... Gladiator (can't find it now) - and this is where I got this games idea from. Nowadays, we have the flash equivalents (but nowhere near as good a game system as the aforementioned Gladiator RPG): Galdiator2 flash game


Greetings. I have long followed the forum here but never posted. Thank you, Mr. Hicks for creating this museum for us to enjoy. I also enjoyed the pics of your various world travels. :-)

I think I have a source of inspiration for a game of this nature. My first computer was an Apple IIe and on that machine we had a game called Arena of Octos. It was a turn based gladiator game set in a sci-fi setting.

Mark, good luck in creating your game.


OK, use printing functions on the 42S to send game update data via IR to an external box. This box would coordinate game play among several calculators, and update a shared display. The 42S would do control input and have local state displayed. Presto - real time multiplayer. :)

You didn't say it had to be practical :)



Howard - Thanks for the idea! Another practical idea - how about a pinball simulator? The program continuously calculates where the ball should be on the table and reports this using distance from a base point. The player then uses a tape measure to position the ball on the table and keeps this updated as the program calculates each new position. I'd call it something like "Slowball".


OK, use printing functions on the 42S to send game update data via IR to an external box. This box would coordinate game play among several calculators, and update a shared display. The 42S would do control input and have local state displayed. Presto - real time multiplayer. :)

You didn't say it had to be practical :)





Texas Hold'em. Could be interesting AI work.

Slot machine. Brain dead simple.


Thanks everyone for the interesting ideas!!! :)

I'm sorry to say that I am not going to do anything remotely like a Dungeons and Dragons game. My feelings towards that game are not printable. Nothing personal and not trying to sound ungrateful for the ideas but "D&D" is a no-go area. If I roll my special one-sided dice, it says "run like hell!!".

Chess - now that is interesting. I had thought about that and a simple one-move lookahead might be feasable. However, lots of available moves need lots of available memory and I'm not sure how this would work out. Still not discounting it though.

Slot Machine - another interesting idea but I don't know much about how they work as I've never played one! Presumably, just a low probability of winning?

Other areas I am trying to think of involve card games or board games where the program would report a move which the player updates on a real board. Chess would be an example but maybe someone can think of a good board game where moves can easily be described.

In terms of program speed, I realise the 42s is not exactly a racehorse so the intended fallback is Thomas Okken's emulator or Christoph's one if I can work the 42s ROM dump.

Any more ideas hugely welcome! :)



Years ago I taught an intro programming course and assigned games as the coursework. The "big" project was to implement the game called Black Box where the computer would randomly hide N balls in an 8x8 grid and you had to guess the location by probing from the edge of the board. Probes had one of three results: hit, reflection or exit out of a different edge location, Wikipedia has all the details.

It's a good programming exercise and a fun game to play. It's likely impossible to play it all in your head but easy to print it out or write it out on scratch paper as you play.



Very interesting idea, I like it! Thanks Katie. One thing that isn't clear to me from the rules though is when you get a hit, is the ball location revealed? Or do you just get told it is a hit with no ball revealed?

One aspect concerns me with doing this on a 42S is the limited vertical display height. Although I have never played it, I get the impression that being able to see the entire board is quite important. If you include the row/column results, that means finding a way of representing a 10x10 board on a display with 16 vertical pixels. I've got a few ideas on this though...

Thanks again for the great suggestion!



A hit is simply indicated by marking the edge position that you probed from. The balls are only revealed at the end of the game. You need to have some mechanism to tell the computer/calculator where you think the balls are. When you're satisfied that you have them all located correctly you then tell the machine that you're done -- it revels the true location and scores how you did based on how many probes you made and if you have any incorrect guesses (this is described in the wikipedia).

Yes, you really do need to see the board all at once.
A 10x10 (including edge labels) is needed and you need to allow for some way the player can indicate where he/she thinks the balls are located within the grid. You might be able to do a very little bit of vertical scrolling to allow the user to see more than a couple of bits for each location in the grid. Too much scrolling will make this very difficult to play. It's going to be a challenge to do this on a 16 bit display. A printer output option would be very useful.

Edited: 15 July 2009, 2:39 a.m. after one or more responses were posted


Thanks Katie. I did read through the Wiki page on this game but it left quite a few holes in exact mechanics of the game. Be patient please - I will have some more questions. Thanks!



How about Sudoku? You could do it in 3 stages:

  1. User inputs the known values, then guesses the unknowns. The program validates each guess and (of course) tells them when they've solved the puzzle
  2. Use inputs the known values and the program solves the puzzle. There are plenty of sites that describes algorithms for solving the puzzle and I can provide C++ source code for my own if you like.
  3. Program creates a board for the user (or program!) to solve.


Thanks for the idea David. I can see a nice way of implementing a sodoku board in 3x3 blocks on the 42s display. Certainly one to give some serious consideration - but if I did it, I would have to write my own solving algorithms, no cribbing! It would be a matter of principle to work out how to do it, especially as I have never ever played the game (but I know the rules).



How about the Fifty Game?

Two players (or one player and the computer) take turns, each entering a number from 1 to 6. A running total is established. The person who hits exactly 50 is the winner.

If you analyze the game, you will realize that the player who goes first will always win if he/she knows the "secret" and doesn't make a mistake. If the first player does not know the secret, but the second player (computer, in this case) does, then there is a very high probability that the second player will win.

My middle school kids love this game, and I always tape a one dollar bill above the board and offer it to whomever can beat me (I go second). I always end up losing the dollar when one of the bright ones figures out the secret.


Sounds like Nim ( IIRC, there are a few RPN versions of this around.

Mathematics Magazine a few months back had a great article on non-transitive dice games. Basically there are 4 dice, each has different numbers on the sides. Each dice has a probability of besting the other dice, e.g. A > B > C > D, however D > A. So in this game it is the person that goes 2nd that has the upper hand. Play that with your kids, best of ten, each time allow them to pick any dice first, you'll win almost every time. Even if you alternate you'll still have the advantage.

Now if they can figure out how that works, well then you truly have a gifted student.

Edited: 27 June 2009, 11:49 a.m.


Thanks Don. As Egan has already said, this looks a bit like a Nim variation. Is that correct or have I misunderstood the concept? Certainly, the idea is a really good one for a calculator and as it isn't the classic matchstick Nim game, it would be new and worth doing. I shall consider this one. Thanks for the suggestion!



Yeah, Egan is right, it is similar to Nim. I programmed the 50 game on my 12c in 67 steps. If you win, the final display says 55178 ("bliss" upside-down). If the calculator wins it says 3507.1 ("I lose"). I got that idea from an old HP-65 NIM game!


I've always enjoyed the game Daleks. It's a very simple turn-based strategy game, but quite engaging. I'd explain further, but I'm typing this on my phone - Google should turn up numerous implementations and explanations. The 42s graphics capabilities would probably be just enough to pull it off.


Great game. It was also called Robots. I built the BSD "robots" version for my Mac. Given all today's gaming choices, its the simple games that I find most enjoyable.

I tried to create a 41CX version using the 32 column HP-IL Video interface, but screen updates were too slow and the 41CX is just too slow for interactive games. I may try a 71B version using the 80 column HP-IL Video interface. Versions exist for the 50g.

There are a number of Star Trek turn-based games available that may also workout well. Graphics are not necessary, but providing updates on a printer may be nice (see example below). Think of "Trek" as a much more engaging version of the board game Battleship. There are many C-based (e.g. BSD) and BASIC versions around to base an RPN version on. Actually there is an RPN version already for the 41CX ( Build on that.

Example BSD printer output:

Short range sensor scan
0 1 2 3 4 5 6 7 8 9
0 . . . . # . . @ . . 0 stardate 2800.05
1 . . . . . . . . . . 1 condition GREEN
2 . . . . . . . . . . 2 position 5,6/5,5
3 . . . . . . . . . . 3 warp factor 5.0
4 . . . . . . . . * . 4 total energy 5000
5 * . . . . E . * . * 5 torpedoes 10
6 . . . . . . . . . . 6 shields up, 100%
7 . . . . . . . . . . 7 Klingons left 6
8 . . * . . . . . . . 8 time left 7.95
9 . . . . . . . * . . 9 life support active
0 1 2 3 4 5 6 7 8 9
Starsystem Beta III
For the most part BSD Trek is like the 41CX Trek, but with more options and strategy. Both versions are line oriented, but the BSD version has short range and long range sensor commands than print the above output.

A 42S version of this would be very nice.

Edited: 28 June 2009, 10:12 a.m.


I just want to say a huge thank you to everyone who came up with ideas here. Lots of interesting thoughts including some which will translate on other machines (need to spend some time on the 85).

I had to select one idea of course and the one I've selected is Katie's Black Box suggestion. Currently, I am working on testing out a few program mechanics to find out how I am going to implement the program with the 42s functionality as well as mapping out all the features I want to implement. I've got a clear vision for how I want it to look and work at least. Displaying the board is going to be main contentious area but I think my solution will work.

Anyway, time to start work :)



That sounds great, Mark. Good luck, and please post the results when you're done so we can all marvel at your work :)



looking forward to your game implementation, it looks like a great idea. One more to throw in which would definitely be above the capabilities of the display is Risk. Thinking of students, it might be interesting to play a game of risk say with the 50 states. Clearly the players would have to have a map of the US in their head. The better you know the map, the higher your chances of winning. Extensions to different maps (Americas, world, even the stars with a number of constellations as the 'map') are possible. It could be a fun game to play and teach something at the same point.



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