What is "double"

The floating point is used to represent fractional values or when a range greater than that given by the fixed point (of the same bit width) is required, even at the cost of accuracy. Double precision can be chosen when the range or accuracy of "single precision" is insufficient.

Double allows the representation of numbers between 10^-308 and 10³⁰⁸, with a total accuracy of 15 to 17 decimal digits.