set serveroutput on
set verify off
declare
	grade char(1) := upper('&grade');
	appraisal varchar2(20);
Begin
	appraisal :=
		CASE grade
			when 'A' then 'excellent'
			when 'B' then 'very good'
			when 'C' then 'Good'
			else 'No such grade'
		end;
	dbms_output.put_line('Grade is := ' || grade || ' appraisal is :- ' || appraisal);
end;

bcm@bcm-laptop:~$ sqlplus user1/user1

SQL*Plus: Release 11.2.0.1.0 Production on Thu Jul 26 09:43:09 2012

Copyright (c) 1982, 2009, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

09:43:09 SQL> @code
09:43:13 SQL> set serveroutput on
09:43:13 SQL> set verify off
09:43:13 SQL> declare
09:43:13   2  	      grade char(1) := upper('&grade');
09:43:13   3  	      appraisal varchar2(20);
09:43:13   4  Begin
09:43:13   5  	      appraisal :=
09:43:13   6  		      CASE grade
09:43:13   7  			      when 'A' then 'excellent'
09:43:13   8  			      when 'B' then 'very good'
09:43:13   9  			      when 'C' then 'Good'
09:43:13  10  			      else 'No such grade'
09:43:13  11  		      end;
09:43:13  12  	      dbms_output.put_line('Grade is := ' || grade || ' appraisal is :- ' || appraisal);
09:43:13  13  end;
09:43:13  14  /
Enter value for grade: A
Grade is := A appraisal is :- excellent

PL/SQL procedure successfully completed.

09:43:17 SQL>