VMS Help TCPIP Services, Programming Interfaces, RPC XDR Routines, xdr_double, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    A filter primitive that translates between double-precision
    numbers and their external representations.

    This routine is actually implemented by four XDR routines:
    xdr_       converts VAX D-format floating-point numbers
    double_D
    xdr_       converts VAX G-format floating-point numbers
    double_G
    xdr_       converts IEEE T-format floating-point numbers
    double_T
    xdr_       converts IEEE X-format floating-point numbers
    double_X
    You can reference these routines explicitly or you can use
    compiler settings to control which routine is used when you
    reference the xdr_double routine.