65. Ripple Carry Adder

How do you plan to solve it?

// 1-bit Full Adder (to be used by the 4-bit RCA)
module full_adder_1bit (
    input  a, b, cin,
    output sum, cout
);
    // TODO: implement 1-bit full adder (structural or dataflow)
    wire w1,w2,w3;
    xor x1(w1,a,b);
    xor x2(sum,w1,cin);
    and a1(w2,a,b);
    and a2(w3,w1,cin);
    or o1(cout,w2,w3);

endmodule

// 4-bit Ripple Carry Adder – chain 4 full adders
module rca4_chain (
    input  [3:0] a,
    input  [3:0] b,
    input        cin,
    output [3:0] sum,
    output       cout
);
   wire x,y,z;
    // TODO: Declare internal ripple carries
    full_adder_1bit fa1 (.a(a[0]), .b(b[0]), .cin(cin), .sum(sum[0]), .cout(x));
    full_adder_1bit fa2 (.a(a[1]), .b(b[1]), .cin(x), .sum(sum[1]), .cout(y));
    full_adder_1bit fa3 (.a(a[2]), .b(b[2]), .cin(y), .sum(sum[2]), .cout(z));
    full_adder_1bit fa4 (.a(a[3]), .b(b[3]), .cin(z), .sum(sum[3]), .cout(cout));
     
    // TODO: instantiate 4 full adders and chain carries


    // TODO: drive cout


endmodule