ADDER USING 4-TO-1 MUX

module adder_using_4to1_mux(

                             input [1:0]ab,input carry_in,clk,

                             output reg sum,carry_out

    );

           

          /// declaring parameter

parameter  SEL_LINE_1 = 2'b00;

parameter  SEL_LINE_2 = 2'b01;

parameter  SEL_LINE_3 = 2'b10;

parameter  SEL_LINE_4 = 2'b11;

           

           

always@(*)                         // (*) means sensitivity list contains all the right side values

begin

if(ab==SEL_LINE_1) begin

          sum <= carry_in;

          carry_out <= 0; end

          else if(ab==SEL_LINE_2) begin

          sum <= ~carry_in;

          carry_out <= carry_in; end

          else if(ab==SEL_LINE_3) begin

          sum <= ~carry_in;

          carry_out <= carry_in; end

else

          begin

          sum <= carry_in;

          carry_out <= 1;

          end

end

endmodule