Need assistance

[mm0fmf]

On 18/07/2015 18:34, Mark Lawrence wrote:
>
> What is an {HP calculator} roll operation?

HP calculators were proper in that they used RPN entry.

i.e. 2 enter 2 + would show 4 instead of 2 + 2 =

Gawd it's so long but ISTR there were 3 stack registers and the display. 
So you could press

1 enter
2 enter
3 enter
4

and Z = 1, Y = 2, X = 3 and display = 4. Roll would rotate the entries 
through the display register.

ROLL and Z = 2, Y = 3, X = 4 and display = 1

and so on. There was an INV ROLL to go the other way.

The 3 level stack was equivalent to nesting parentheses three times. I 
only had a TI-59 as it was half the price of an HP67. The TI had more 
memories and program steps and was faster. But it didn't say HP on the 
front!