PL/SQL run from SQL*Plus

  Hi Folks,

          I wish to run a PL/SQL script from SQL*PLUS. However   I am getting error messages such as:-   

    Unknown command beginning "Cursor .." rest of line ignored

  This occurs for each of the PL/SQL commands. I have appended the script   below.

  My Questions are (1) Can PL/SQL be run as a script from SQL*PLUS ?


                   (2) If so, what are the syntax requirements to do this ?


                   (3) What system changes are needed.



  All help will be very welcome.

                               Many Thanks,
                               
                                      Michael.

  declare CURSOR C1 IS
  SELECT I.SESSION_CODE,req_TIME,X_LENGTH,FULL_SESS,

         START_TIME,MINS,EXAM_DATE

  FROM   I.INVIG_SESSION I,X_SESSION X
  WHERE  I.SESSION_CODE = X.SESSION_CODE
  AND    X.SESSION_CODE IN (SELECT SESSION_CODE
                            FROM INVIG_SESSION
                            WHERE INVIG_SESSION.STUD_NO = '123456');

        FETCH C1 INTO CREC;
        EXIT WHEN CREC%NOTFOUND;
        MESSAGE (CREC.I.SESSION_CODE);