1 files changed, 51 insertions, 0 deletions
diff --git a/source/arduino/bitwisexornot.rst b/source/arduino/bitwisexornot.rst
new file mode 100644
index 0000000..25389cb
--- /dev/null
+++ b/source/arduino/bitwisexornot.rst
@@ -0,0 +1,51 @@
+.. _arduino-bitwisexornot:
+
+Bitwise NOT (~)
+===============
+
+The bitwise NOT operator in C++ is the tilde character ~. Unlike &
+and \|, the bitwise NOT operator is applied to a single operand to
+its right. Bitwise NOT changes each bit to its opposite: 0 becomes
+1, and 1 becomes 0. For example:
+
+
+
+::
+
+        0  1    operand1
+
+
+
+::
+
+       ----------
+        1  0   ~ operand1
+
+
+
+::
+
+        int a = 103;    // binary:  0000000001100111
+        int b = ~a;     // binary:  1111111110011000 = -104
+
+
+
+You might be surprised to see a negative number like -104 as the
+result of this operation. This is because the highest bit in an int
+variable is the so-called sign bit. If the highest bit is 1, the
+number is interpreted as negative. This encoding of positive and
+negative numbers is referred to as two's complement. For more
+information, see the Wikipedia article on
+`two's complement. <http://en.wikipedia.org/wiki/Twos_complement>`_
+
+
+
+As an aside, it is interesting to note that for any integer x, ~x
+is the same as -x-1.
+
+
+
+At times, the sign bit in a signed integer expression can cause
+some unwanted surprises.
+
+