The KEY attribute can be applied to record  fields  to  indicate
  that  the  field is to be used as a key field when the record is
  part of an indexed file.

  Syntax:

     KEY [[( n [[, {options},... ]] )]]
     KEY [[( {options},... )]]

  The 'n' represents the key number.  A key number of 0  indicates
  that  the field is the primary key of the record.  All other key
  numbers indicate alternate keys.   The  key  number  must  be  a
  constant  expression  that denotes an integer value in the range
  from 0 through 254.

  See the "HP Pascal Language Reference Manual" for  the  complete
  description of using the KEY attribute.

1  –  Options

  You can specify certain characteristics of  the  record  key  by
  listing  the  desired  options on the KEY attribute.  With these
  options, you can control the order of the collating sequence and
  you can allow changes or duplicates on a key.

  See the "HP Pascal Language Reference Manual" for  the  complete
  description of using these options.

1.1  –  ASCENDING

  This option, along with DESCENDING, allows you  to  specify  the
  collating  sequence  for the key field.  By default, the primary
  key and alternate key are ASCENDING.

  When creating a new file, Pascal will create the  key  with  the
  collating  order  specified.  When opening an existing file, the
  Run-Time Library will verify that the existing key  matches  the
  collating  order  specified.  If neither ASCENDING or DESCENDING
  is specified when opening an existing file, both types  will  be
  accepted.

1.2  –  CHANGES

  This option allows you to specify that changes can be  performed
  on the key.

  The default for the primary key is NOCHANGES and the default for
  alternate  keys  is  CHANGES.   You  can override the CHANGES on
  alternate keys with NOCHANGES.  It is illegal to specify CHANGES
  on the primary key.

  When opening an  existing  file,  the  Pascal  Run-Time  Library
  ignores this option.

1.3  –  DESCENDING(see ASCENDING)

1.4  –  DUPLICATES

  This option allows you to specify that duplicates of the key are
  allowed.

  The default for the primary key is NODUPLICATES and the  default
  for alternate keys is DUPLICATES.

  When opening an  existing  file,  the  Pascal  Run-Time  Library
  ignores this option.