A powerful all round calculator (Casio FX 991ES)

Member Name: hurdygurdyman

Product:	Casio FX 991ES
Date:	02/07/09 (72 review reads)
Rating:

Advantages: Capable of most functionality except graphs, can be typed in a natural way, gives numbers precisely

Disadvantages: Input lag, complex number functionality not perfect

I bought this calculator just over a year ago with the intention of using it in exams, specifically A levels. I was a little worried it would not be allowed at first, because as other reviewers have noted, it is a very powerful calculator, however the only rule set by the JCQ (who regulate A levels, GCSEs and some vocational exams) is that the calculator must not be capable of symbolic calculus (note that this may change in time, but for my session was accurate).

However, this calculator is still very powerful. It provides far more functionality than the average user would need. This includes numerical integration and differentiation, which if used by someone who knows what they are doing, is as useful as symbolic calculus, as a confirmation.

This is also the main disadvantage of the calculator - for all it is capable of, the old computer adage of Garbage In, Garbage Out still applies. The end user needs to understand the maths behind what they are doing, and the calculator offers no functionality to assist this in any way.

The other major problem is a "lag" in long calculations. For example, in large fractions, possibly including summations (sigma), the screen redraws itself after every input, and will not accept any other input in this time. This means that if you are trying to type 222, then the last 2 might be missed, causing the result to be out by an order of magnitude. This is a problem that has cost me marks, and so when using the calculator it becomes vital to double-check calculations.

One final problem is mainly caused by the calculator's other function. When typing a calculation such as the square root of 8 or 2pi, the calculator is knowledgeable enough to display these in standard form - 2(square root sign)2 and 2pi respectively - this is the form that is most useful for a mathematician. However, it does not extend this functionality to any logarithms (the calculator can do any base of logs) or exponentials, displaying these as decimals. This is particularly a problem in advanced calculus where it is more useful to have the natural logarithm function.

In conclusion, despite a number of problems, there is no doubt that this is an excellent calculator. GCSE students thinking of taking any A level mathematical subjects (which includes the sciences) would be well advised to purchase this, probably in addition to a graphical calculator. Physicists might also find its database of constants useful. However, for other students, cheaper alternatives might serve them better, and for an average end user just interested in calculating VAT, this is not a suitable calculator.

Summary: Probably the best calculator on the market, despite some problems.