// Half Adder primitive
module half_adder (
input a, b,
output sum, carry
);
assign sum=a^b;
assign carry=a&b;
endmodule
// Full Adder using 2 Half Adders
module full_adder_struct (
input a, b, cin,
output sum, cout
);
wire w1,w2,w3;
half_adder h1(a,b,w1,w2);
half_adder h2(w1,cin,sum,w3);
or o1(cout,w2,w3);
endmodule