HP-15C expanded memory firmware: problems with matrix larger than 8x8

[J-F Garnier]

Ouch ! You frightened me Eric with your post subject. I thought you found a new problem in the expanded memory firmware.

Fixing the known problem with matrix larger than 8x8 and operations involving the LU decomposition would be nice for sure, even if I'm not sure there is a real practical need for it.

For me, the main benefit of the expanded memory versions is that we don't have any practical memory limitation.

With the standard 64-register version, using two 4x4 matrices leaves only 14 registers for programming, but not even enough for integration.
With the 192-reg expanded version, we can have two matrices up to 8x8 (128 reg.), use the complex mode (5 reg.) and the solve&integrate features (23 reg.), and still have 18 registers (126 bytes) for a non-trivial program.

However, your idea to trigger Error 11 in case of a matrix > 8x8 is interesting, it would protect unaware users from potentially bad consequences.
This would be consistent with the other minor limitations of the extended versions:
- we can't allocate more than 99 storage registers,
- we can't create a matrix with more than 99 elements in a row or column,
both cases that trigger Error 10 and so are harmless.

It remains the (IMHO minor) bug with program steps beyond 999 , especially step 1000 that is displayed as: " 000-000000"
Any way to limit the steps to 999?

[Edit:]
While we are at it, it would be nice to improve the MEM display for configurations with more than 99 free/program registers.
Currently, this is displayed with my patch as, e.g. " 19164 10-0" or " 19 64110-0"
Not so difficult to read when we are used to it, but may be confusing for new users.
It would be nice to add a '.' separator such as " 19.164. 10-0" or " 19. 64.110-0"
but I didn't try to do it at the time.

J-F