Verilog(三) multiplexer

module  mux4_1(sel, din0, din1, din2, din3, dout);
  input  [1:0]  sel;
  input    din0, din1, din2, din3;
  output  dout;
  reg   dout;

always @ (sel or din0 or din1 or din2 or din3)
begin
  case(sel)
    2‘b00:  dout = din0;
    2‘b01:  dout = din1;
    2‘b10:  dout = din2;
    2‘b11:  dout = din3;
    default:  dout = din0;
  endcase
end

endmodule