add project03 base files

03/a/Register.hdl

@@ -0,0 +1,17 @@
+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/3/a/Register.hdl
+/**
+ * 16-bit register:
+ * If load is asserted, the register's value is set to in;
+ * Otherwise, the register maintains its current value:
+ * if (load(t)) out(t+1) = int(t), else out(t+1) = out(t)
+ */
+CHIP Register {
+    IN in[16], load;
+    OUT out[16];
+
+    PARTS:
+    //// Replace this comment with your code.
+}