You can invoke CDO as a foreign Digital Command Language (DCL) command.
  At the DCL prompt, type REPOSITORY OPERATOR and any CDO command.  After
  the CDO command executes, you automatically return to the DCL prompt.

  Before invoking CDO with the REPOSITORY OPERATOR command, make sure
  that your CDD$DEFAULT is set to the CDO dictionary that you want to
  work in.  You cannot override your CDD$DEFAULT by using the REPOSITORY
  OPERATOR command.

  You can use the hyphen ( - ) to continue a CDO command that extends
  beyond one line.

  The following command creates the field definition MIDDLE_INITIAL in
  your default dictionary:

  $ REPOSITORY OPERATOR DEFINE FIELD MIDDLE_INITIAL -
  _$ DATATYPE IS TEXT SIZE IS 1.
  $