The SET statement sets values of indexes associated with table
  elements.  It can also change the value of a conditional variable,
  change the status of an external switch, and store the address of a
  COBOL identifier reference at run time.

  Format 1 -

  SET { rsult } ... TO val

1 - rsult

  is an index-name, the identifier of an index data item, or an
  elementary numeric data item described as an integer.

2 - val

  is a positive integer, which may be signed.  It can also be an
  index-name (or the identifier of an index data item) or an elementary
  numeric data item described as an integer.