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Can anyone explain the useage by HP of "F" and "G" keys for function keys? Why were these letters chosen? Also, it looks like the new 49G+ has "left" and "right" arrow keys for other key functions. Why not F and G?

I have always assumed that this was "f" for function key, and originally this was the only one. Later HP added a second one and used "g" as it was the next letter. "h" appeared in the HP-34C.

I have no evidence for this, just my own speculation.

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Can anyone explain the useage by HP of "F" and "G" keys for function keys? Why were these letters chosen?

It's mathematical notation. In math one uses the notation f(x) and g(x) to denote functions. The notation f-1 is also mathematical, meaning the inverse function of f. I believe the HP-65 was the only one ever to have f-1.

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Also, it looks like the new 49G+ has "left" and "right" arrow keys for other key functions. Why not F and G?

Beats me. I've never liked those angular arrows myself; it would have been enough to have unlabeled, colored shift keys.

By the way, the colors gold and blue initially chosen by HP of the Golden Era were wise choices; color-blind people are likely to be unable to distinguish between green and red, but yellow and blue are okay. But then the Golden Era ended and all sorts of "in style" colors appeared, all the way to the (ugh) teal and lavender of the HP-48G/GX.

-Ernie

Just a comment: "h" first appeared in the HP 67, long before the HP 34.

While "f(x)" and "g(x)" are usual mathematical function notation (as is "f-1(x)"); the letter selection also fit nicely with the A,B,C,D,E definable keys on the HP 65 and 67. This may have been infuenced by the physical layout of the handhelds (5 top row keys).

The need for a sixth top row key, as in the Pioneers, with A...F meaning, is very convenient for hexadecimal functions; but this doesn't seems to have been an important concern before 1980. If "F" means binary 1111 or decimal 15, then the function key should be labeled differently.
The angled "left shift" and "right shift" keys are compatible with this. Personally, I don´t like them, but one must concede that such arrows are a blessing for persons with color blindness.

Texas Instruments calculators have had [2nd] from the very start. In recent years, calculators such as the TI-36X have added [3rd].

I find it amusing that TI has always used gold for [2nd] and now blue for [3rd] -- a copycat color scheme from HP calculators.

One advantage of TI's shift key naming scheme over HP's is that HP's uses up letters that _may_ collide with other key labels, while TI's choice is unlimited ("Press [17th] and [x25] to raise a number to the 25th power"). For example, if the HP-67 had to have another shift key, it couldn't be named [i] because that's already used in financials and, in more modern machines, for the imaginary unit.

-Ernie

```Ernie Malaga wrote:
> For example, if the HP-67 had to have another shift key,
> it couldn't be named [i] ...
```

Of course, because the HP-67 and 97 already use the letter
i for the index register. In fact the HP97 has an I key (in the HP-67 the function of the I key is replaced by composite instrustions, i.e. STI rather than STO I).

**vp