I've used the ability to compile the WP 34S firmware on my computer to create a number of small patches for it. These aren't bug fixes in any sense; rather, they are small pieces of code that change the behaviour of the WP 34S calculator in various ways. I've made them to make my favourite calculator even better (at least, from my point of view!) I'm sharing them here in case anyone else is interested.

Links to the patch files are at the bottom of the page, along with instructions for use.

Here is a description of each patch.

1. New “Casio style” fraction separator. This is simple: on old 7-segment Casio calculators fractions were displayed with _| as the separator. I remember this from my childhood, and so this patch changes the WP 34S fraction separator to the old Casio style.

2. “Casio style” exponent key behaviour. On older Casio calculators pressing the exponent key when a number was expected - e.g., after CLEAR or an arithmetic operator - would enter PI, without the need to use the shift key. Doing this on the WP 34S doing this enters “1 EEX”; this behaviour is standard on HP machines. I prefer the Casio behaviour and so this patch emulates it on the WP 34S.

Note: in program mode, this changed behaviour persists. This means that this patch will break code (written by you or a third party) that depends on the standard HP behaviour.

Note 2: in program mode the key still displays as EEX even though it acts as PI.

3. Double-dot fraction entry. On the HP-32SII, pressing 3 . . 7 enters the fraction 3/7. On the WP 34S, the same key sequence enters 3 0/7. This is logical, but it kept on tripping me up. This patch implements the double-dot entry on the WP 34S.

Note: when the second dot is pressed, the dot already entered changes to the lower half of a comma to indicate the double press.

Note 2: once again, code depending on the standard behaviour will be broken by this patch. Such code is unlikely to be common.

4. A new display mode. The new mode (which takes over the standard behaviour of the ALL display mode) formats numbers to a number of significant figures chosen by the user. Unlike SCI or ENG mode, exponent notation is not used unless the number is outside the range 10^(-3) to 10^(10), and by default trailing zeros are removed. So entering PI and successively multiplying it by 10 would display (in ALL 5 mode): 3.14159; 31.4159; 314.159; 3,141.59; 31,415.9; 314,159; 3,141,590; 31,415,900; 314,159,000; 3.14159e9; and repeated division by 10 would give: 0.314159; 0.0314159; 0.00314159; 3.14159e-4.

The advantages of this mode are that it doesn't drown you in significant figures, extra zeros, or exponent notation. It might seem strange (on a calculator with a double precision mode!) to deliberately hide significant figures, but I like it. I often use ALL 3 (4 significant figures) when doing physics calculations; I rarely need to see more digits than this.

If you would prefer trailing zeros, setting user flag K will give them. So in mode ALL 2 the number “3” would display either as 3 or as 3.00 depending on the state of flag K.

Selecting ALL 10 or ALL 11 turns off the effect of flag K on the display.

Note: SHOW and RND still work as expected.

5. y-register displayed in dot matrix portion of the display. The mighty HP-42S calculator displays the y-register contents on the top line of its 2-line whenever possible. Other HP calculators (e.g., HP 33S, HP 35S) do the same thing. The display on the WP 34S just isn't as flexible as a full dot-matrix display, but it's long enough to display quite a few digits. This patch displays a properly-formatted version of the y-register in the dot-matrix part of the WP-34S display, during digit entry and when results are displayed.

Note: Alpha-mode display and messages are not affected.

Note 2: In integer mode the y-register is not displayed; mode and bit number (e.g., 2c64) is shown as normal.

Note 3: y-register contents are displayed in decimal mode even when the main display is in fraction or HMS mode.

Note 4: When an exponent is needed for y-register display the mantissa is truncated, not rounded.

Note 5: Double precision mode is handled with four digits of exponent display, if needed, but for four digit exponents the “e” is replaced by a colon for positive exponents and removed completely for negative exponents.

Note 6: the y-register display replaces certain information normally displayed in that area - grad angle mode, and MM.DDYYYY display mode. These annunciators are still visible when a function shift key is pressed.