|HP-15C/32S/42S top-row math keys |
Message #20 Posted by Karl Schneider on 26 Sept 2009, 6:41 a.m.,
in response to message #19 by Mike Morrow
I find it interesting that the 32s has e^x and ln as primary functions (with 10^x and log10 shifted), but the 42s has log and ln (with 10^x and e^x shifted). Which came first, and why the change?
I suspect the design differences are evidence that the HP42S was not related to the HP32S in any way except use of Saturn and external appearance.
"not related ... in any way"? That's a rather sweeping -- and wrong -- conclusion based on just one difference in key layout.
Use of the Saturn microprocessor is a significant similarity because that means identical mathematical algorithms (for functions that are common to both). The virtually-identical appearance resulted from the use of identical packaging and basic layout, as well as a design based on one shift key and menu-based access to many functions.
Of course, the function set, display, programming paradigm, and price were quite different.
As for the minor difference in top-row keys: The HP-42S has an unshifted up-arrow key (convenient for menu and program scrolling), bumping XEQ to the top row and leaving one fewer key for transcedental math functions. This also explains why yx was shifted. (Walter B. correctly pointed out that the layout of these keys are identical to those of the HP-41.)
Back to the original poster's question: The square-root symbol (x inside a radical) can be difficult to discern in small font. That may explain why square root, instead of x2, is typically unshifted.
I suspect that aesthetics and consistency of structure played a large role in some of the layouts:
UNSHIFTED: sqrt ex 10x yx 1/x
SHIFTED: x2 LN LOG % %CHG
UNSHIFTED: sqrt ex LN yx 1/x
SHIFTED: x2 10x LOG % %CHG
UNSHIFTED: 1/x sqrt LOG LN
SHIFTED: yx x2 10x ex
The following should be noted:
- On the HP-15C, the three leftmost pairs are inverse functions, and the three "exponentiated to power x" functions are side-by-side, forming a group.
- On the HP-42S, the three rightmost pairs are inverse functions. Four exponentiated functions are side-by-side, as are LOG and LN. These also form groups.
- The HP-32S is perhaps optimized for convenience; LN and ex-- which are used more than LOG or 10x -- are unshifted on two of the five keys.
Edited: 26 Sept 2009, 10:10 p.m.