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HP Forum Archive 20

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Message #1 Posted by Jake Schwartz on 14 Apr 2011, 10:50 a.m.


First, let me say that I have read the 1.16 and 1.17 manuals many times....but I have some questions regarding use of ALPHA: 1. If I fill ALPHA with more characters than can be displayed at once and only the right-hand end is shown, how do I get to view the left end again? Is there any way to scroll ALPHA left and right, like with integers? At least the HP41 did automatic scrolling when ALPHA was larger than the display. 2. The manual indicates that alpha-STO stores the leftmost 6 characters into a destination, but after doing ASTO 00 (for instance), a RCL 00 only shows me a numeric value and not the six characters I expected to see. Nothing I could find in the manual indicates how ALPHA characters are stored (or encoded) in a numeric register. If there is any insight into these items, I'd appreciate hearing it.

Thanks, Jake

Re: wp34S ALPHA
Message #2 Posted by Marcus von Cube, Germany on 14 Apr 2011, 11:27 a.m.,
in response to message #1 by Jake Schwartz

Windowing the alpha register is still under discussion and will be implemented somehow. Scrolling will not.

The companion to aSTO is aRCL which has to be done in alpha mode or from a program. It might be a useful addition to allow a range of numeric registers be stored from and recalled to alpha, at least two for the full display length. To be negotiated...

A short explanation: Until now, registers are not tagged as containing alpha or integer or HMS data or whatever. So a RCL always interprets the contents as a real number with strange effects.

Re: wp34S ALPHA
Message #3 Posted by Walter B on 14 Apr 2011, 3:10 p.m.,
in response to message #1 by Jake Schwartz


Alpha is - in a way - the ugly duckling in this project. It took some effort to get in even the standard alpha operations of the 42S. It isn't complete yet.

Answer 1: As Marcus mentioned, alpha scrolling is waiting for implementation, so the respective description on page 52 of the recent documentation is only wishful thinking so far (though it shows our plans). The sample string of page 24 (v1.17) was carefully keyed in and documented in parallel :-)

Answer 2: Whatever you store using alphaSTO, you may recall with alphaRCL. We've also added a new command alphaRC# for appending numbers to the string as well. Please check and play, it's working fine IMHO.


Edited: 14 Apr 2011, 3:12 p.m.

Re: wp34S ALPHA
Message #4 Posted by Paul Dale on 14 Apr 2011, 7:02 p.m.,
in response to message #1 by Jake Schwartz

As has been mentioned alpha-RCL is needed. There simply isn't space in our registers to have a flag indicating alpha data or not. We might be able to squeeze this into reals with a bit of trickery but there is no chance for integers which also support alpha STO and RCL operations.

Alpha characters are stored as their byte values first character highest. The number of characters varies in integer mode based on the current word size. The function that does this is basically:

	z = 0
	n = #characters per register

for i = 1 to n z = (z * 256) + alpha[i] return z

Take some alpha data and reduce it modulo 256 to extract the characters again.

- Pauli

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