bac nao lam roi chi minh voi

code:
LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
ENTITY vidu IS
PORT(a, b, en : IN std_logic;
q0, q1, q2, q3 : OUT std_logic);
END vidu;
ARCHITECTURE Vtructural OF vidu IS
COMPONENT inv
PORT(a : IN std_logic;
b : OUT std_logic);
END COMPONENT;
COMPONENT and3
PORT(B1, B2, B3 : IN std_logic;
o1 : OUT std_logic);
END COMPONENT;
SIGNAL nota, notb : std_logic;
BEGIN
I1 : inv
PORT MAP(a, nota);
I2 : inv
PORT MAP(b, notb);
B1 : and3
PORT MAP(nota, en, notb, Q0);
B2 : and3
PORT MAP(a, en, notb, Q1);
B3 : and3
PORT MAP(nota, en, b, Q2);
B4 : and3
PORT MAP(a, en, b, Q3);
END Vtructural;

may bao loi:



gio minh can lam gi de may co the chay duoc.