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+.. _arduino-bitshift:
+
+bitshift left (<<), bitshift right (>>)
+=======================================
+
+Description
+-----------
+
+From *The Bitmath Tutorial* in The Playground
+
+
+
+There are two bit shift operators in C++: the left shift operator
+<< and the right shift operator >>. These operators cause the bits
+in the left operand to be shifted left or right by the number of
+positions specified by the right operand.
+More on bitwise math may be found
+`here. <http://www.arduino.cc/playground/Code/BitMath>`_
+
+
+
+Syntax
+------
+
+variable << number\_of\_bits
+
+
+
+variable >> number\_of\_bits
+
+
+
+Parameters
+----------
+
+variable - (byte, int, long) number\_of\_bits integer <= 32
+
+
+
+Example:
+--------
+
+::
+
+        int a = 5;        // binary: 0000000000000101
+        int b = a << 3;   // binary: 0000000000101000, or 40 in decimal
+        int c = b >> 3;   // binary: 0000000000000101, or back to 5 like we started with
+
+
+
+When you shift a value x by y bits (x << y), the leftmost y bits in
+x are lost, literally shifted out of existence:
+
+
+
+::
+
+        int a = 5;        // binary: 0000000000000101
+        int b = a << 14;  // binary: 0100000000000000 - the first 1 in 101 was discarded
+
+
+
+If you are certain that none of the ones in a value are being
+shifted into oblivion, a simple way to think of the left-shift
+operator is that it multiplies the left operand by 2 raised to the
+right operand power. For example, to generate powers of 2, the
+following expressions can be employed:
+
+
+
+::
+
+        1 <<  0  ==    1
+        1 <<  1  ==    2
+        1 <<  2  ==    4
+        1 <<  3  ==    8
+        ...
+        1 <<  8  ==  256
+        1 <<  9  ==  512
+        1 << 10  == 1024
+        ...
+
+
+
+When you shift x right by y bits (x >> y), and the highest bit in x
+is a 1, the behavior depends on the exact data type of x. If x is
+of type int, the highest bit is the sign bit, determining whether x
+is negative or not, as we have discussed above. In that case, the
+sign bit is copied into lower bits, for esoteric historical
+reasons:
+
+
+
+::
+
+        int x = -16;     // binary: 1111111111110000
+        int y = x >> 3;  // binary: 1111111111111110
+
+
+
+This behavior, called sign extension, is often not the behavior you
+want. Instead, you may wish zeros to be shifted in from the left.
+It turns out that the right shift rules are different for unsigned
+int expressions, so you can use a typecast to suppress ones being
+copied from the left:
+
+
+
+::
+
+        int x = -16;                   // binary: 1111111111110000
+        int y = (unsigned int)x >> 3;  // binary: 0001111111111110
+
+
+
+If you are careful to avoid sign extension, you can use the
+right-shift operator >> as a way to divide by powers of 2. For
+example:
+
+
+
+::
+
+        int x = 1000;
+        int y = x >> 3;   // integer division of 1000 by 8, causing y = 125.
+
+