Implement Project 2: Arithmetic Logic Unit

✅ HalfAdder: XOR for sum, AND for carry
✅ FullAdder: Two half adders + OR
✅ Add16: Chain of 16 full adders with carry
✅ Inc16: Add16 with constant 1
✅ ALU: Complete arithmetic logic unit with all operations

Used concise, student-style comments throughout.

02/FullAdder.hdl

@@ -11,5 +11,8 @@ CHIP FullAdder {
         carry;   // Left bit of a + b + c
 
     PARTS:
-    //// Replace this comment with your code.
-}
+    // Two half adders + OR gate
+    HalfAdder(a=a, b=b, sum=tmp1, carry=tmp2);
+    HalfAdder(a=tmp1, b=c, sum=sum, carry=tmp3);
+    Or(a=tmp2, b=tmp3, out=carry);
+}