VMS Help PASCAL, Predeclared Routines, Arithmetic, ABS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The ABS function returns a value (of the same data type  as  the
  specified   parameter)   that  is  the  absolute  value  of  the
  parameter.

  Syntax:

     ABS( x )

  The parameter 'x' can be of any arithmetic type.