CASIO fx-991CW

[Dave Britten]

Just got my fx-991CW today, and I've found/confirmed a few rather important improvements:

1. You can now change the auto power off time to either 10 minutes (default) or 60 minutes. This is big - I've seen plenty of complaints about losing work due to the older fx-991EX powering off automatically. Now you can change it to 60 minutes and not have to worry about this happening nearly as much.
2. Spreadsheet data now survives switching modes. There may be exceptions to this, but I was able to go to stat mode, enter some two-variable data, and switch back and forth between the two apps without data in either app being deleted. (The ON key will still clear the spreadsheet.)
3. As mentioned, stat mode also retains its data when switching modes, but more significantly, data is also retained when powering off. Please correct me if I'm wrong, but I don't think this was the case on the ES or EX families.
EDIT: 4. And I just noticed that the spreadsheet has 40% more memory available compared to the EX: 2380 bytes free vs. 1700. But it's also storing higher-precision values, with each numeric cell entry consuming 14 bytes instead of 10. But since formulas are still seemingly stored as character strings with one byte per character, you should theoretically be able to fit more into memory if your sheet is using a lot of formulas. Both the EX and CW store both the formula definition and the result value for each cell, but the formula definition portion at least should consume a smaller portion of total RAM now.

Alas, the CALC button and multi-statement (the colon) appear to be well and truly gone. But given that you can now define two functions f(x) and g(x), and the spreadsheet's data is now more durable, I suspect many of the use cases of CALC and multi-statement can be satisfied by using these two other functions instead, perhaps to even better effect than the old functions. Set your auto-power-off time to 60 minutes, put a few formulas into the spreadsheet, enter variable values to get results, switch to other modes as needed, come back to the spreadsheet to tweak the variables a bit more, etc.

Those who extensively use engineering display or engineering symbols should probably steer clear of the CW. Entering engineering symbols requires pressing Catalog, using the page/arrow keys to scroll to "Engineer Symbol", then scrolling through the list of symbols to the one you want. And they're spelled out with full names, (e.g. "Femto", "Milli"), all capitalized, which is rather disorienting for the ones that are typically written with a lowercase abbreviation. If you want to shift the mantissa and exponent of a result up and down - a task you would accomplish with a pair of "ENG" keys on older Casios - you have to press "Format", select "ENG Notation", then use the left and right arrow keys to adjust the exponent. All in all, it's wildly unwieldy compared to dealing with engineering display on almost every other Casio I've used. If Casio had at least designed this to open the Catalog and Format menus with the cursor defaulting to the last-used item, that would have gone a long way to improving things (and not solely in this situation).

In general, that seems to be the theme: if you hate the TI-36X Pro because of its heavy reliance on menus, the fx-991CW is definitely not going to win you over. But if you don't mind menus, or if you find the very busy keyboard of the fx-991EX somewhat confusing, you'll find that the CW has good discoverability, and a keyboard that isn't overly cluttered. (e.g. the single "Format" key instead of two ENG keys, a fraction/decimal key, and a degrees-minutes-seconds key)