p-variable at HP9825

[William]

I would like know more about p-variable at HP9825. My questions:

• are the p-variables just an option or are they available by default?

• are the p-variables in 9825 model A or model B or both?

• what is the benefit of using p-variables and r-variables?

[ronaldo]

I have tested on my 9825A:
25 -> p1
and got error A5.
My 9825A has General I/O - Extended I/O ROM, Matrix ROM and String - Adv. Programming ROM. The 4th ROM slot is empty. Maybe another ROM is needed. The p-variables exists. I have found two old reports (one from NASA) with description of p-variables.