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

  ABS (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   |  ABS    | IIABS    | INTEGER*2  | INTEGER*2   |
  |      |         | JIABS    | INTEGER*4  | INTEGER*4   |
  |      |         | ABS      | REAL*4     | REAL*4      |
  |      |         | DABS     | REAL*8     | REAL*8      |
  |      |         | QABS     | REAL*16    | REAL*16     |
  |      |         | CABS     | COMPLEX*8  | REAL*4      |
  |      |         | CDABS    | COMPLEX*16 | REAL*8      |
  |      |         | ZABS     | COMPLEX*16 | REAL*8      |
  +------+---------+----------+------------+-------------+
  See also the IABS intrinsic function.