Unexpected Feature on HP-22

[rprosperi]

It's interesting that this is *not* in the manual. I discovered it in the past probably by just playing with the machine (though it may have been discovered on an HP-80 as I owned that first) but, like you, probably skipped the 'number entry' section when working through the manual.

You can easily achieve the entry of very small numbers using a variation of this same technique as follows:

Enter 10000000000... until you get to the positive magnitude of the negative exponent you want
[ENTER]
1
[X<>Y]
[/]
Mantissa
[X]

So, to get 4.556 E-15, do

1000000000000000 (that's 15 zeros)
[ENTER]
1
[X<>Y]
[/]
4.556
[X]

You lose the T register, but otherwise it gets it done.

These days, it seems the very large numbers are needed by financial folks dealing with National Debt issues, but the very smallest numbers only when dealing with effective interest rates earned at your local bank.

This makes one wonder how many other features we all 'know' aren't in the manuals at all.