WP-34S: Little issue with program step indicator

[Miguel Toro]

Hello,

I noticed a strange behavior with my WP-34s (3.2 3450):

Say, I do not have any program in RAM, then the indicator shows 527 steps available for programing in my calculator. After executing some chosen program in the library (TVM, MIO for example), the calculator shows 526 steps, so one step less. I tried some things:

- CLP does not change anything (still 526 instead of 527)

- Creating an instruction and deleting it gives back the missing step.

- CLPALL also returns to the 527 steps available.

- Some library instructions do not alter the step indicator, for example any vector routine: V.V or V+V, they both behave :-)

That is it. Just curious on why executing some programs in the library alters the program step indicator.

Thanks and regards,

Miguel.

[Barry Mead]

I believe that the memory available for program steps is shared with the memory used to create local memory variables. So if a library function makes use of local variables, that would decrease the reported "Free Steps" shown. This is mentioned on page 173 of the printed manual (or page 154 of the pdf version).

Edited: 5 Sept 2013, 3:15 p.m.

[Miguel Toro]

Thank you Barry.

But how does that explain that creating and then deleting just one instruction, makes the indicator come back to normal? Deleting an instruction also clean the local variables?

Thanks,

Miguel

[Paul Dale]

I am pretty sure that deleting a program step clears the return stack which includes all local variables. If it didn't, all the return addresses would be incorrect after the delete. Marcus would know for sure.

- Pauli

[Miguel Toro]

Thank you Pauli. I forgot about the return stack.

Regards,

Miguel

[Marcus von Cube, Germany]

I've yet to check what the exact reason is for the vanishing program step. The explanations so for seem correct. You can easily clear the return stack with the sequence g RTN from the keyboard. Check if this sequence "repairs" the free memory display.

[Miguel Toro]

Hi Marcus,

Yes, It does indeed.

Thank you and regards.

Miguel