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)
    assign sum = a^b^cin;
    assign cout = (a&b)|(b&cin)|(cin&a);

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
);
    // TODO: Declare internal ripple carries
    wire [3:0]w;;
    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit f1(.a(a[0]),.b(b[0]),.cin(cin),.sum(sum[0]),.cout(w[0]));
    full_adder_1bit f2(.a(a[1]),.b(b[1]),.cin(w[0]),.sum(sum[1]),.cout(w[1]));
    full_adder_1bit f3(.a(a[2]),.b(b[2]),.cin(w[1]),.sum(sum[2]),.cout(w[2]));
    full_adder_1bit f4(.a(a[3]),.b(b[3]),.cin(w[2]),.sum(sum[3]),.cout(w[3]));
    // TODO: drive cout
    assign cout=w[3];

endmodule