OpenVMS usage:floating_point
    type:         F_floating, D_floating, G_floating, H_floating,
                  IEEE S_floating, IEEE T_floating
    access:       write only
    mechanism:    by value

    Result of raising a floating-point base to an unsigned longword
    integer exponent. OTS$POWRLU returns an F-floating number.
    OTS$POWDLU returns a D-floating number. OTS$POWGLU returns a
    G-floating number. OTS$POWSLU returns an IEEE S-floating number.
    OTS$POWTLU returns an IEEE T-floating number.

    On VAX systems, OTS$POWHLU_R3 returns an H-floating number.