Which calculators had no known bugs?

[teenix]

(11-13-2017 01:33 PM)PANAMATIK Wrote:  Finally I discovered a bug in the HP-29C, which I didn't have seen mentioned before.

If you enter all 98 program steps numbers and run, the program can't be interrupted. You have to switch off the calculator.

This is also the case in my HP-29C Low Power emulation, but because it never can be switched off even when the batteries are removed, it hangs forever. I had to add a special "Reset" procedure for this case.

Bernhard

That is true and it isn't true. :-)

I cannot fully test this because I do not have a real HP-29c.

Looking at the microcode, during a running program, the HP29c doesn't test for a key press when it is executing these programmed keys...

0 - 9, CLx, EEX and CHS

Therefore, if your program, which uses all steps, has only these keys, it will not be able to be stopped. This is unlikely in a real program though.

Any other programmed key allows testing for a keypress in the microcode and therefore stops the program.

The power switch is always supposed to stop a running program. As far as I can tell during a running program, there is nothing in the microcode that tests Status Flag [5], which is the power switch test, so there must be some other mechanism to stop the program.

In my emulator, I assumed that Status Flag [2] is cleared by hardware on switch off. This always stops and resets a running program and the calculator jumps into it's power off code loop.

cheers

Tony