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

  The PRED function returns  the  value  preceding  the  parameter
  according to the parameter's data type.

  Syntax:

     PRED( x )

  The parameter 'x' can be of any  ordinal  type;  however,  there
  must be a predecessor value for 'x' in the type.