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) | (a & cin) | (b & 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 carry1, carry2, carry3, carry4;
    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit fullAdder1(a[0], b[0], cin, sum[0], carry1);
    full_adder_1bit fullAdder2(a[1], b[1], carry1, sum[1], carry2);
    full_adder_1bit fullAdder3(a[2], b[2], carry2, sum[2], carry3);
    full_adder_1bit fullAdder4(a[3], b[3], carry3, sum[3], carry4);
    // TODO: drive cout
    assign cout = carry4;

endmodule