The UPPER function returns the upper bound  for  ordinal  types,
  SET base types, and array indexes.

  Syntax:

     UPPER( x [[, n]] )

  The parameter 'x'  is  a  type  identifier  or  variable  of  an
  ordinal,  SET,  or  ARRAY type.  The parameter 'n' is an integer
  constant that denotes a dimension of 'x', if 'x'  is  an  array.
  If  'x' is an array and if you omit the 'n', VSI Pascal uses the
  default value 1.  If 'x' is an array, UPPER  returns  the  upper
  bound  of  the nth dimension of 'x'.  If 'x' is an ordinal type,
  UPPER returns the upper bound or largest value.   If  'x'  is  a
  SET, UPPER returns the upper bound of the SET base type.