Buggy Hewlett Packard 15C Scientific Calculator iPhone App?

[Thomas Klemm]

(11-27-2015 01:19 PM)Marcio Wrote:  Well, if the LE still has the bugs of the original, I think the list should be updated so users know what troubles to avoid, especially this one related to the CHS command.

Not sure if there's a list of known HP-15C bugs.

Quote:I can't understand why well-known and discussed-to-death old bugs are not eliminated

Fixing a bug in a ROM is difficult. As far as I know even HP doesn't have the original source files anymore. Thus all you can do is disassemble the ROM to get assembler code. But without comments this tends to be difficult to understand. Just as an illustration here's a method of the HP-48 written in SysRPL (not assembler) that I once tried to understand. Without the comment in the header I wouldn't have had an idea what's going on.
The assembly code often uses tricks that are not apparent. So even if you understand what's going on you still don't understand why it's needed. I once fixed a bug in the ROM of the HP-80. The fix was trivial: I just had to switch a bit. But it took me a long time to find it.
And then even if you find the reason for the bug it's often not that easy to fix it because the fix has to fit in the limited amount of bytes you have in the ROM.

"Life is short and ROM is full."
-- Bill Wickes

In addition to that you want to be sure that you don't introduce another bug with your fix. For this you usually have a suite of tests. But we currently don't have anything like that.

Quote:and new ones are introduced.

The specification for these emulators was probably the existing Nonpareil written in C. Though it's not too difficult to translate that to Java (for Android) or Objective C (for iOS) the part dealing with the GUI had probably to be written from scratch. This explains why most of the bugs are somehow GUI related. I assume that handling the PSE-function had to be rewritten as well. Otherwise the pause would only take a few milliseconds instead of about 1 second if the emulator runs at full speed.

This forum is probably not the correct place to file a bug report. I suggest to try at HP or send a message to Tim or Cyrille.

Cheers
Thomas