beginner: 3:8 decoder with enable

i want to write the architecture of 3:8 decoder with enable ...

anyone can help ,

i wrote the entity

ENTITY Decoder3_8_Enable IS
  port (a: in std_logic_vector(2 downto 0);
        e: in std_logic ;
        y:out std_logic_vector(7 downto 0));
END ENTITY Decoder3_8_Enable;

HaYZaM