ceil() returns the smallest floating-point number of integral
    value greater than or equal to x.

                           Entry-Point Names

    Generic
    Function   Data Type   OpenVMS        Tru64 UNIX
    Name       Required

    ceil       S_FLOAT     math$ceil_s    ceilf
               T_FLOAT     math$ceil_t    ceil
               X_FLOAT     math$ceil_x    ceill
               F_FLOAT     math$ceil_f
               G_FLOAT     math$ceil_g