Complete guide to the SENASA calculator, key by key

What every key of the pilot theory exam calculator does, checked against the official demo. Each section has a link to see it on the replica.

1. What it looks like and how it is operated

The calculator appears in a window inside the exam application and responds to the mouse only: there are no keyboard shortcuts. It has four blocks:

Functions, at the top: sin cos tan ln log, asin acos atan e^x 10^x, x^2 e π √x 1/x and the brackets ( ).
Phone-style keypad: 1 2 3 is on the top row and 7 8 9 on the bottom row, the opposite of a desk calculator. It is the most common slip on exam day.
Operations: + - * /, the sign change +/-, the full clear C and equals =.
Memory: MS MR M+ M- MC.

It always works in degrees; there is no radians mode. And it has no general power key and no scientific notation: how to get round both is explained below.

2. How it writes numbers

It accepts 11 digits per number. From the twelfth digit on it silently stops writing. With decimals, at most 10 digits after «0.». See it on the calculator
Integers are shown with a trailing point: 14 appears as 14.
There is no key to delete one digit. If you mistype a number, press ( and type the right one: the wrong number is discarded and = closes the bracket by itself. See it on the calculator
The sign is changed with +/- after typing the number. If you press it first, the sign disappears as soon as you type the number: 8 * +/- 2 = gives 16 when you wanted −16. See it on the calculator
Long results fit in 12 digits. Very small ones appear as 6.666666666 -8, meaning 6.67×10⁻⁸ with the last digit truncated, not rounded. See it on the calculator

3. The four operations and precedence

Multiplication and division come before addition and subtraction, as in maths: 2 + 3 * 4 = gives 14, not 20. But three behaviours are not those of a normal calculator:

A subtraction followed by × or ÷ and then another + or − groups wrongly: it subtracts everything that follows. 10 - 3 * 2 + 1 = gives 3 instead of 5, and 100 - 50 / 2 - 10 = gives 85 instead of 65. Fix: put the multiplication or division in brackets, 10 - ( 3 * 2 ) + 1 =. See it on the calculator
Two operations in a row are not replaced. If you press the wrong operation and then the right one, the calculator keeps both and repeats the previous number: 2 + * 3 = gives 8 (it does 2 + 2 × 3) and 5 + = gives 10. If you press the wrong operation, press C and start again. See it on the calculator
Pressing = repeatedly does not repeat the operation. 2 + 3 = = is still 5. See it on the calculator

4. Brackets

They can be nested. A ) with no open ( works out everything pending, as if it were equals: 2 + 3 ) * 4 = gives 20. And the other way round: = closes every bracket still open. See it on the calculator
It does not multiply by itself. A number followed directly by a bracket, by π, by e or by MR is lost: 5 ( 2 + 3 ) = gives 5, not 25, and 2 π gives 3.1415…, not 2π. Always press *. See it on the calculator
Limit of 12 pending operations. Every waiting operation and every open bracket takes one slot, and there are only 12. Once they are full, the screen stops updating with =, ) and the operations, and the calculator seems dead. C gets you out. In long calculations, work in parts and store intermediate results with MS. See it on the calculator

5. Sine, cosine and tangent

Number first, then the function: 30 sin gives 0.5. If you press sin before the 30, it is applied to the 0 that was on screen. See it on the calculator
Everything in degrees. The inverses asin acos atan return degrees.
Results are rounded to 4 decimals, and the calculator keeps working with the rounded value. With small angles it shows: 1 tan * 60 = gives 1.05 when the real value is 1.047. It cannot be avoided; pick the closest answer. See it on the calculator
The most expensive bug in the exam: if the result of a trigonometric function is the second number of an addition, the calculator glues it on instead of adding it. 1 + 30 sin = gives 10.5 instead of 1.5. The same happens if you recall it from memory with MR or if it is inside brackets. Fix: start the operation with the function, 30 sin + 1 =, or multiply the result by 1 before adding. See it on the calculator
90 tan gives no error: it shows a 17-digit number. If you see something like that after a tangent, check the angle. See it on the calculator

6. Logarithms, exponentials and powers

ln is the natural logarithm and log the base-10 one; e^x and 10^x are their inverses. x^2 squares, √x takes the square root and 1/x the reciprocal. All are pressed after the number.
There is no x^y key. For any other power: base log * exponent = 10^x. For example 3⁴: 3 log * 4 = 10^x gives 81. See it on the calculator
There is no scientific notation. To enter 5×10⁶: 6 10^x * 5 =. See it on the calculator
π and e are constants: they replace whatever is on screen. For 2π you must type 2 * π =. See it on the calculator
A result that is too large gives Error: 1000 e^x. See it on the calculator

7. The memory

MS stores the number on screen, MR recalls it, M+ and M- add to or subtract from what is stored and MC clears it.
C does not clear the memory, and there is no «M» on screen to tell you something is stored. Before using M+, press MC if you are not sure. See it on the calculator
M+ also «glues» trigonometric results, and the memory stays contaminated: the next M+ glues too, even with a normal number. 2 M+ 30 sin M+ MR gives 20.5 instead of 2.5. To store a sine or cosine use MS, or multiply it by 1 first. See it on the calculator

Safe method for long calculations: MC when you start, solve each part, MS to store the result, and MR where you need it.

8. When «Error» appears

Dividing by zero, the square root of a negative, or asin and acos of a number greater than 1.
After an Error in the middle of an operation, everything keeps giving Error however much you type: 1 / 0 + 5 = gives Error. Press C and start again. See it on the calculator
NaN.00000NaN is a different thing: it is what the screen shows when the calculator has frozen because of the 12 pending operations (section 4).

9. How to practise with this guide

The PilotKeys calculator behaves like the exam one in the 597 of 597 cases we compared against the official demo. With the Study helper on you see your formula as the calculator understands it and a warning when you type something in an order that does not work. When the exam is a few days away, switch to Exam mode, which removes the aids and leaves the calculator with its real look, and run a round of the timed training. The eight rules that avoid the bugs in this guide are summarised on the golden rules sheet, and the typical exam formulas, key by key, in the worked examples.