--model of CLA unit
entity cla4b is
	port(g, p :in bit_vector (3 downto 0);
		 cin : in bit;
		cout : out bit_vector (4 downto 0);
		gout, pout : out bit
		 );
end entity cla4b;

architecture cla_arch of cla4b is
	begin
		cout(0) <= cin;
		cout(1) <= g(0) OR (p(0) AND cin);
		cout(2) <= g(1) or (g(0) and p(1)) or (cin and p(0) and p(1));
		cout(3) <= g(2) or (g(1) and p(2)) or (g(0) and p(1) and p(2)) or (cin and p(0) and p(1) and p(2));
		cout(4) <= g(3) or (p(3) and g(2)) or (p(3) and p(2) and g(1)) or (p(3) and p(2) and p(1) and g(0)) or (p(3) and p(2) and P(1) and p(0) and cin);
		gout <= g(3) or (p(3) and g(2)) or (p(3) and P(2) and g(1)) or (p(3) and P(2) and p(1) and g(0));
		pout <= p(3) and p(2) and P(1) and p(0);
		
		end architecture cla_arch;