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) | (a & cin);
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 c0,c1,c2,c3,c4;
    assign c0 = cin;
    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit a0(.a(a[0]),.b(b[0]),.cin(c0),.sum(sum[0]),.cout(c1));
    full_adder_1bit a1(.a(a[1]),.b(b[1]),.cin(c1),.sum(sum[1]),.cout(c2));
    full_adder_1bit a2(.a(a[2]),.b(b[2]),.cin(c2),.sum(sum[2]),.cout(c3));
    full_adder_1bit a3(.a(a[3]),.b(b[3]),.cin(c3),.sum(sum[3]),.cout(c4));
    // TODO: drive cout
    assign cout = c4;

endmodule