|11C/15C keyboard layout and functions|
Message #14 Posted by Karl Schneider on 11 Mar 2006, 5:21 p.m.,
in response to message #13 by Valentin Albillo
Hi, Valentin --
Yes, indeed the layout and organization of the HP-15C keyboard (based, of course, on that of the HP-11C) is an absolute marvel of coherent thought and organization. Even after adding a substantial amount of functionality for the 15C, the grouping of functions on the keyboard was actually improved somewhat over the 11C. Note the following improvements on the 15C over the 11C:
- All statistical functions (except CLEAR SIGMA) are on the bottom row
- All three conversion functions are side-by-side
- Pi and its shift key are closer together
- x<>(i) and x<>I were replaced by a more-versatile "x<> "
Another bit of good thinking was to place SOLVE above the "divide" key, which is used for solving an exactly-determined linear system of equations.
So, if one could revisit 1981-1982 to improve the HP-15C (as well as other Voyagers, respectively), how could that have been done without changing its hardware or paradigm in any way? Fixed specifications include the following: Voyager packaging; 7-segment, 10-digit display; RAM; ROM space; microprocessor; and battery.
We've discussed this before, a few archives ago, with the question framed a bit differently. I can think of only the following improvements to the HP-15C within the limitations I have specified:
Place LN and ex on keys 12 and 13, rather than ex and 10x
This was implemented on the successor Pioneer-series models. Perhaps there was a pleasing symmetry with ex, 10x, and yx side-by-side. Also, keycodes 11, 12, 13, 22, 23, 24, and 25 all had blue-shifted inverses of transcedental functions (maybe that was the reason!). However, LN is just more useful than 10x.
Show A, B, C, D, and E in program keycodes where appropriate (for labels and matrix identifiers), rather than the corresponding positional keycodes 11, 12, 13, 14, and 15.
This was implemented on the Pioneer-series HP-20S, but might have run into issues of development time and ROM space for the HP-15C.
Move CLx above the backarrow as a yellow-shifted function, put "SHOW" or "MANT" as the blue-shifted function, and perform "CLEAR PREFIX" as on the HP-41 and the Pioneer-series models: by re-pressing the shift key.
Clearing a prefix key by performing a "no op" or "display mantissa" function was probably carried over from the LED-display Spice models such as the HP-34C, which had no annunciator for a shift key. I believe that considerable 34C microcode was ported to the 11C, which in turn was used in the 15C.
That's about it. For what the HP-15C was, those are about the only feasible improvements I can think of -- absolute perfection was nearly achieved. Certainly, a few other functions would have been useful, such x-estimator (present on the HP-10C and HP-12C), y1/x, x2, and "ALL" display format. However, there just wan't available space, at least without resorting to key combinations that were arcane, unintuitive, or inconvenient.
BTW: What are the seven uses of the [+] operation? I can identify four, six, or eight, depending on how one is counting:
Two real scalars
Two complex scalars
One matrix and one real scalar (in either order)
STO + (real scalar to numbered register or matrix element)
RCL + (real scalar from numbered register or matrix element)
Edited: 11 Mar 2006, 5:28 p.m.