Casio FX-991ES Calculator

As Head of Maths at my school I have recently been recommending this model to all my A Level and Further Maths students. As others have said, this model seems to have taken as a starting point the regulations for calculators to be permissible in exams and then pushed the features right up to the boundary. Matrix and Complex Number calculations seem particularly useful, and the Summation of a Series between two integer limits is very handy for checking in exams. I usually recommend that for A Level a student takes TWO calculators into the exam (including one for graphing) with this being the 'workhouse' machine for the majority of the paper. A very comfortable size, and an unbeatable price.

Well.
Since meeting Cas (that's what we call him)my life has taken a turn for the better. I used to slave away over the older Casio models - striving for that one line integration. Now, life is golden. Integration? Pppfftt.... seconds! Quadratics? For breakfast! Natural logarithms? A joy!
With Cas riding in my pocket, I swagger into exams.
Only problem with this little whipper-snapper is his constant thirst for vintage past-paper questions. We're running out of years and money! It's not cheap to relive the glory days! Mum and Dad are having to make up questions.
You will never get caught off guard running out of charge - the wizards of Casio truly had thought of everything when they installed the solar power feature.
Stunning interface - there is such a thing as love at first sight! My parents were a bit apprehensive about buying me it. They thought I'd get distracted from my books - they know how I get about these things!
The instruction manual makes for light-bedtime reading. When you get into it, it's like a Steven King thriller! I never tire of discovering Cas' new features - she surprises me at every turn - every question is an opportunity for revelling in the delights of this little beauty's astounding capabilities.
One evening, as I wept into my pot noodle, Cas jumped out at me. My mood was instantly lightened upon my discovery of its degree features. Smooth transition between degrees, radians and gradians put a grin on my face, matched only by that of the Chesire cat.
Not only that, this calculator looks stunning - it goes well with any outfit, whether you are strolling into the exam hall or simply prowling the streets at night (those ladies can't resist my mathematical prowess). However, the Crème de la crème is when one is seen with a well-tailored Armani suit, mid-heeled wing tips, and cheeky Cas poking out the shirt pocket, ready for action.
In conclusion, this calculator has revolutionised modern life for me - it is my family, my friend, it is my life and soul. I live and breath Cas - it's the quintessential calculator that you can pop out on the bus and have a wee play with when you're bored. Boredom soon becomes an archaic memory. Just remember, it NEEDS to sleep in a physics data booklet otherwise he's grouchy in the morning!

Adieu.

I've always owned Casio calculators. I've still got one which is 25 years old! Any time I've used other makes I find the layout or method of operation hard to get used to.

I'd resisted buying a new calculator for a long time as I'm one of the "oldies" who has become used to the "immediate execution" input method of the older models, but time moves on, and you can't deny that the rationale of the newer "perfect algebraic logic" models is more sensible.

This is the top non-graphic model Casio currently make. It does pretty much everything you're ever likely to want from a non-programmable, non-graphic calculator. However, I feel the ease-of-use has been compromised in various ways that makes me wonder if a more basic model would actually be better:

This model supports seven independent memories, which is nice, but sadly the normal scratch-memory found on simple models now requires two/three keypresses to access (SHIFT-STO-M or RCL-M), just the same as the other six memories. Bring back "M in" and "MR" buttons!

It can use the content of the other six memories to do simplistic algebraic equation solving. However, the input method in this mode is so cumbersome it's actually quicker to scrawl a bit of algebraic rearrangement on a scrap of paper and work it out yourself.

The same applies to many of the other "helpful" modes, although one could argue the Matrix mode is useful to avoid user error with the long-hand method, although it will only support 3x3 matrices maximum.

There are a large number of useful physical constants and conversion factors built-in, but they have missed a trick by not presenting them by name, instead requiring you to enter them by number (there's a crib-sheet on the inside of the sliding case), *after* which it will tell you the name of (but not the value of) your chosen factor!

The distinguishing marketing feature of this model is supposedly its ability to display the maths you're inputting in a more natural form. Sadly it doesn't really even manage to do that properly, as you have to press special keys to get one-over-the-other division layout, and a far too frequent use of the cursor keys to jump about within that layout. Yet it doesn't in reality gain you anything if you know the slightest thing about algebra in the first place, as you'd simply use the standard divide key and parenthesis.

Overall, whilst this model has a comprehensive feature-set and is quite nicely made, I can't help but feel it is aimed at students with little skill in maths in an effort to allow entry of poorly-understood textbook/exam question and provide an answer. For the more average maths-capable student or someone in full-time work who needs a slick calculation tool to do the donkey-work of some complex problem, you end up using this calculator in a manner similar to one of the lesser models (i.e. direct line-entry of the basic functions), completely ignoring any of the relatively exotic features of this larger-screen model.

Conclusion: Decent, but ultimately flawed and overly cumbersome. Not enough focus on basic usability, with some obvious missed opportunities to utilise the large screen for the best.