Arithmetic Operators (+, -, *, /)

The operators +, -, *, and / respectively evaluate to the sum, difference, product, or quotient (respectively) of the two operands. The operation is conducted using the data type of the operands, so, for example, 9 / 4 gives 2 since 9 and 4 are int variables.

This also means that the operation can overflow if the result is larger than that which can be stored in the data type (e.g. adding 1 to an int with the value 2,147,483,647 gives -2,147,483,648).

If the operands are of different types, the “larger” type is used for the calculation. If one of the numbers (operands) are of the type float or of type double, floating point math will be used for the calculation.


The specifics of these rules are beyond the scope of this documentation; for more information, see The C++ Programming Language, by Bjarne Stroustroup, Appendix C, especially §§C.4-C.6, or this WikiBooks entry on C++ type conversion.


For more information on how computers represent integers, see the Wikipedia page on two’s complement.


y = y + 3;
x = x - 7;
i = j * 6;
r = r / 5;


result = value1 + value2;
result = value1 - value2;
result = value1 * value2;
result = value1 / value2;


value1: any numeric variable or constant

value2: any numeric variable or constant

Programming Tips

  • Know that integer constants default to int, so some constant calculations may overflow (e.g., 200000 * 5000000 will yield a negative result).
  • Choose variable sizes that are large enough to hold the largest results from your calculations.
  • Know at what point your variable will “roll over” and also what happens in the other direction e.g. (0 - 1) for unsigned arithmetic, or (0 - -2,147,483,648) for signed arithmetic.
  • For math that requires fractions, float variables may be used, but be aware of their drawbacks: large size and slow computation speeds (the STM32 has no floating point hardware, so all floating point calculations have to be done in software).
  • Use cast operator, e.g. (int)myFloat to convert one variable type to another on the fly.

Arduino Compatibility

Since the STM32 processor on the Maple is a 32-bit machine, the int type overflows at a much higher value on Maple than on Arduino. In particular, on Maple, ints do not overflow (become negative) until they reach 2,147,483,648; on the Arduino, they overflow at 32,767. Because of this, programs running on Maple are much less likely to run into overflow issues. The following table summarizes the sizes and ranges of integer datatypes on the Maple (the ranges of long long types are approximate):

Datatype Unsigned range Signed range Size (bytes)
char 0 — 255 -128 — 127 1
short 0 — 65,535 -32,768 — 32,767 2
int 0 — 4,294,967,295 -2,147,483,648 — 2,147,483,647 4
long 0 — 4,294,967,295 -2,147,483,648 — 2,147,483,647 4
long long 0 — 1.8*1019 (approx.) -9.2*1018 — 9.2*1018 (approx.) 8

See Also

License and Attribution

Portions of this page were adapted from the Arduino Reference Documentation, which is released under a Creative Commons Attribution-ShareAlike 3.0 License.