Declare variables for the tuning parameters displaystyle mathbf{K_P, K_I} and displaystyle mathbf{K_D} as floats. This means that each of the variables can take on a range of values from displaystyle mathbf{pm 3 imes 10^{38}}.
Declare variables to store the input, output and set point as doubles. For Arduino double is the same as float. However, true double precision uses twice as much storage space. Therefore a larger range of values may be represented.