Remove demo directory

projects/demo/Xor.cmp

@@ -1,5 +0,0 @@
-|   a   |   b   |  out  |
-|   0   |   0   |   0   |
-|   0   |   1   |   1   |
-|   1   |   0   |   1   |
-|   1   |   1   |   0   |

projects/demo/Xor.hdl

@@ -1,25 +0,0 @@
-// 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/demo/Xor.hdl
-
-/**
- *  Exclusive-or gate: true if either a is true and b is false, or
- *  a is false and b is true; false otherwise.
- *  QUESTION: how can the simulator execute this program properly without
- *  HDL implementations of the underlying Not, And, and Or chip-parts?
- *  Answer: since the demo folder contains no Not.hdl, And.hdl and Or.hdl
- *  files, the simulator reverts to using their built-in implementations.
- */
-
-CHIP Xor {
-    IN a, b;
-    OUT out;
-
-    PARTS:
-    Not (in=a, out=nota);
-    Not (in=b, out=notb);
-    And (a=a, b=notb, out=x);
-    And (a=nota, b=b, out=y);
-    Or (a=x, b=y, out=out);
-}

projects/demo/Xor.tst

@@ -1,29 +0,0 @@
-// 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/01/Xor.tst
-
-load Xor.hdl,
-output-file Xor.out,
-compare-to Xor.cmp,
-output-list a%B3.1.3 b%B3.1.3 out%B3.1.3;
-
-set a 0,
-set b 0,
-eval,
-output;
-
-set a 0,
-set b 1,
-eval,
-output;
-
-set a 1,
-set b 0,
-eval,
-output;
-
-set a 1,
-set b 1,
-eval,
-output;