How To Write PL/SQL block using User-defined Exception Handling

INPUT

declare

            mno A1.ano%type;

            mbal A1.balance%type;

            bal number(5);

            oper varchar2(1);

            exnull exception;

            min exception;

            pragma exception_init(exnull,00100);

begin

            mno:=&mno;

            oper:='&oper';

            select balance into mbal from A1 where ano=mno;

            bal:=&bal;

            if oper='c' then

                        update A1 set balance=balance+bal where ano=mno;

            elsif oper='d' then

                        mbal:=mbal-bal;

                        if mbal<500 then

                                    raise min;

                        else

                                    update A1 set balance=balance-bal where ano=mno;

                        end if;

            end if;

exception

            when exnull then

                        dbms_output.put_line('there is no account of no'||mno);

            when min then

                        dbms_output.put_line('balance is less than 500 so cant debite sucessful');   

end;

/

OUTPUT

1)

Enter value for mno: 10

old  10:  mno:=&mno;

new  10:  mno:=10;

Enter value for oper: c

old  11:  oper:='&oper';

new  11:  oper:='c';

Enter value for bal: 1000

old  13:  bal:=&bal;

new  13:  bal:=1000;

there is no account of no10

PL/SQL procedure successfully completed.

2)

Enter value for mno: 105

old  10:  mno:=&mno;

new  10:  mno:=105;

Enter value for oper: d

old  11:  oper:='&oper';

new  11:  oper:='d';

Enter value for bal: 6000

old  13:  bal:=&bal;

new  13:  bal:=6000;

balance is less than 500 so cant debite sucessful

PL/SQL procedure successfully completed.