VMS Help FORTRAN, Intrinsic Procedures, IABS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  IABS (number)

  A function that returns the absolute value of the argument.  The
  absolute value of a complex number, (X,Y), is the real value (X**2
  + Y**2)**(1/2).

  +------+---------+----------+------------+-------------+
  | Args | Generic | Specific |  Argument  | Result Type |
  +------+---------+----------+------------+-------------+
  |  1   |  IABS   | IIABS    | INTEGER*2  | INTEGER*2   |
  |      |         | JIABS    | INTEGER*4  | INTEGER*4   |
  +------+---------+----------+------------+-------------+
  See also the ABS intrinsic function.