module ha( a, b, cout, sum);
input    a, b;
output  cout, sum;

assign  cout = a & b;
assign sum = a ^ b;

// xor    g1 (sum, a, b);
// and   g2 (cout, a, b);

endmodule




`timescale 1ns / 1ns
module ha_tb;

reg       a,  b;
wire     cout, sum;


ha   u1 ( a, b, cout, sum );




initial begin
         {a, b} = 2'b00;
  #10 {a, b} = 2'b01;
  #10 {a, b} = 2'b10;
  #10 {a, b} = 2'b11;
  #10 $stop;
end

initial $monitor($time, "ns, a=%b, b=%b, cout=%b, sum=%b", a, b, cout, sum);

endmodule