// Half Adder primitive
module half_adder (
input a, b,
output sum, carry
);
xor g1(sum,a,b);
and g2(carry,a,b);
endmodule
// Full Adder using 2 Half Adders
module full_adder_struct (
input a, b, cin,
output sum, cout
);
wire s1,c1,c2;
half_adder dut1(a,b,s1,c1);
half_adder dut2(s1,cin,sum,c2);
assign cout = c1 | c2;
endmodule