module dec2to4 ( d, y);
input   [1:0]  d;
output [3:0]  y;

wire  [1:0]  w;

not g1(w[0],   d[0]);
not g2 (w[1],  d[1]);

// not  (w[0],   din[0]), (w[1],  din [1]);

and g3 (y[0], w[1], w[0]);
and g4 (y[1], w[1], d[0]);
and g5 (y[2], d[1], w);
and g6 (y[3], d[1], d[0]);

endmodule




`timescale 1ns / 1ns
module dec2to4_tb;

reg   [1:0]   din;
wire [3:0]   dout;


dec2to4   uut ( .d(din), .y(dout) );



//dec2to4  uut ( din, dout) ;

initial begin
         din = 2'b00;
  #10 din = 2'b01;
  #10 din = 2'b10;
  #10 din = 2'b11;
  #10 $stop;
end

initial $monitor($time, "ns, din=%b, dout=%b", din, dout);

endmodule