This function returns the maximum exponent used in the model for floating-point numbers of the kind of X.

This is an inquiry function, so X need not be defined; indeed, it is permitted to be disassociated, unallocated, or absent.

The model for real type is that it may be zero or a signed fraction between 1 and 1/RADIX(X) consisting of DIGITS(X) digits, multiplied by an exponent RADIX(X)**e with MINEXPONENT(X)≤e≤MAXEXPONENT(X).

Note that the parameters of the model for real type are chosen so that it most closely reflects the actual floating-point numbers on the machine, but nearly all machine floating-point systems differ from the model in important respects. For example, in IEEE arithmetic, which is the most common floating-point available on modern hardware, there are additional values that lie outside the model; these are infinities, NaNs (Not-a-Number), and subnormal numbers (subnormal numbers have an exponent less than MINEXPONENT(X) but have less precision than model numbers).