av lab4 pb3

module fac(input x, y, ci,
           output co, z);
    assign {co,z}=x+y+ci;
endmodule

module add2b(input [1:0] x, y,
                      input ci,
                      output [1:0] z,
                      output co);

        wire c1;
    fac fac1(.x(x[0]), .y(y[0]), .ci(ci), .z(z[0]), .co(c1));
        fac fac2(.x(x[1]), .y(y[1]), .ci(c1), .z(z[1]), .co(co));

endmodule


module add2b_tb;
    reg[1:0] x, y;
    reg ci;
    wire[1:0] z;
    wire co;
    add2b add2b_i(.x(x), .y(y), .ci(ci), .co(co), .z(z));
    integer k;
        initial begin
            $display("Time\tx\ty\tci\t\tco\tz");
            $monitor("%0t\t%b\t%b\t%b\t\t%b\t%b", $time, x,x, y,y, ci, co, z,z);
            for (k = 0; k < 32; k = k + 1) begin
                    {x,y,ci} = k;
                    #10;
            end
        end

endmodule