Here are my answers to the quiz I posted earlier today (subject: "Quiz: HP Voyagers", 29 Aug 2005, 10:21 p.m.)

The are correct to the best of my knowledge, and I do have a working unit and manual for each model in front of me. I have no excuse for any mistakes here!

I may not have stated several of the questions quite specifically enough, but declined to edit the quiz after posting.

**1. Which model(s) provide all twelve conditional tests?**

Answer: The 15C.

By "conditional tests", I refer only to those six possible comparisons of a full *floating-point value* against 0.00 or another floating-point value, for a total of twelve conditional tests. I did not intend to include flag comparison, bit comparison, or loop-counter functions (which also perform a comparison when invoked).

The complete set is

x<0, x<=0, x=0, x!=0, x>=0, x>0, x<y, x<=y, x=y, x!=y, x>=y, x>y.

The 12 tests were provided by placing only two tests on the keyboard, then giving access to the remaining ten via the function TEST, followed by a one-digit code 0-9. This setup used only three keyboard positions.

**2. Which model(s) provide only eight conditional tests?**

Answer: The 11C and 16C.

The set of eight comparisons is identical to that in the HP-34C, omitting x<=0, x>=0, x<y, and x>=y from the complete set of 12.

The challenge of adding to the 15C these four tests missing from the 11C was ironically re-visited nine years later when the Pioneer HP-32SII was created from the HP-32S.

**3. Which model(s) provide only two conditional tests?**

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4. Which model(s) do not provide insert/delete program editing?**

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5. Which model(s) do not provide a "delete digit" function?**

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6. Which model(s) do not provide any loop-counter functions?**

Answer to 3, 4, 5, and 6: The 10C and 12C.

These two models had the rudimentary programming paradigm that was introduced in the short-lived HP-55 of the 1970's. Only overwriting of programmed instructions was allowed -- no insertions or deletions that make programming useful.

Not provided on the 10C and 12C were loop-counter functions (called DSE and ISG on the 11C and 15C; DSZ and ISZ on the 16C). Only two condtional tests (x<=y and x=0) were provided on the 10C and 12C.

These models also lacked the convienient "delete digit" function and introduced on the predecessor HP-41C. "delete digit" is denoted as a backarrow on the 41C, 11C, and 15C; it is denoted as as "BSP" (backspace) on the 16C. In program mode, "delete digit" serves as "delete line".

In my opinion, this limited programming paradigm ought to have been abandoned, rather than carried forward on new lower-end models. The 10C might have found a niche as a non-programmable with more functions.

**7. Which model(s) provide Solve, Integrate, matrix functions, and functions using complex-valued inputs?**

Answer: The 15C.

Addition of this functionality to the already-capable 11C was the main design objective of the 15C. Solve and Integrate had already been introduced on the 34C, but the robust matrix and complex-number functionality was unprecedented.

To add all this capability, in the same package and hardware of the 11C (whose keyboard positions were already fully-occupied) was an impressive achievement. With some sharp thinking, all the functionality was added, even as the keyboard layout was slightly improved!

An excellent HP Journal article from 1983 (available on the MoHPC CD/DVD set) describes the development of the 15C.

**8. Which model(s) provide an "exchange with memory register" function?**

Answer: The 11C, 15C, and 16C.

The 11C and 16C offered x<>(i) and x<>I, which exchanged x direclty with the I register or indirectly with the numbered register referenced in I. The 15C offered an open-ended "x<> ", that could be completed with I, (i), or any numbered register 0-9 or .0-.9 This gave more functionality, saved one keyboard position, and improved keyboard layout.

**9. Which model(s) do not provide trigonometeric functions?**

Answer: The 12C and 16C.

HP's philosophy has been not to include unnecessary functionality in any model designed for a particular purpose. Trig functions are rarely needed in basic finance and computer-science tasks.

**10. Which model(s) do not provide logarithmic or exponential functions?**

Answer: The 16C.

These are provided on the 12C, however, because natural logarithms, base-e exponentials, and the related power function y^x [= e^(x ln y)] have a solid place in finance. A principal P, compounded at annual rate r for one year in n periods yields a final value F:

F = P*[1 + r/n]^n

As n gets ever-larger (infinite compounding),

F = P*e^r

**11. Which model(s) provide a "modulo division" function?**

Answer: The 16C.

It is called "RMD", and not "MOD" as on the other HP calculators.

**12. Which model(s) allow "F" as a program label?**

Answer: The 16C.

To provide its hexadecimal-representation capability, the letter "F" was required. So, F is also made available as a program label. The 16C has this in common with the Pioneer-series HP-20S. (Of course, "F" is also available as a label on HP's alphanumeric or quasi-alphanumeric models.)

**13. Which model(s) provide a y-estimator regression function?**

Answer: The 10C and 12C.

Ironically, for all the other features these models lacked (see questions 3-6), only these Voyager models offered y-estimator!

This was probably due to lack of available keyboard space on the 11C and 15C, which also included regression-analysis functions.

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Hope you enjoyed the quiz, but sorry -- no prize for a perfect score.

-- KS

*Edited: 30 Aug 2005, 3:03 a.m. after one or more responses were posted*