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 {cout, sum} = a + 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 c1, c2, c3, c4;
    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit a1 ( .a( a[0] ), .b( b[0] ), .cin( cin ), .sum( sum[0] ), .cout( c1 ) );
    full_adder_1bit a2 ( .a( a[1] ), .b( b[1] ), .cin( c1  ), .sum( sum[1] ), .cout( c2 ) );
    full_adder_1bit a3 ( .a( a[2] ), .b( b[2] ), .cin( c2  ), .sum( sum[2] ), .cout( c3 ) );
    full_adder_1bit a4 ( .a( a[3] ), .b( b[3] ), .cin( c3  ), .sum( sum[3] ), .cout( c4 ) );
    // TODO: drive cout
    assign cout = c4;

endmodule