Speed. In fast loops we use fixed point maths, but most of what we do is interfacing with relatively slow moving mechnical equipment, like rotating machinery. Servos are generally dual loops, with analogue inside and digital outside loops.

We get answers that need further processing for display or storage at a rate of about 10 a second off our fastest instruments- FP is very convenient for the maths intensive parts- fixed point sine/tan logs anyone ?

All our stuff is in Pascal not 'C'

Steve