Description

   The SOR$BEGIN_SORT routine initializes the sort process by
   setting up sort work areas and provides key specification and
   sort options.

   Specify the key information with the key_buffer argument, with
   the user_compare argument, or in a specification file. If no key
   information is specified, the default (character for the entire
   record) is used.

   You must use the SOR$BEGIN_SORT routine to initialize the sort
   process for the file, record, and mixed interfaces. For record
   interface on input, you must use the lrl (longest record length)
   argument.

   Some of the following condition values are used with different
   severities, depending on whether SORT/MERGE can recover. Thus,
   if you want to check for a specific status, you should use
   LIB$MATCH_COND.