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+.. highlight:: cpp
+
+.. _lang-define:
+
+#define
+=======
+
+``#define`` is a useful C and C++ feature that allows the programmer
+to give a name to a constant value before the program is compiled.
+The compiler will replace references to these constants with the
+defined value at compile time.
+
+This can have some unwanted side effects.  In general, the :ref:`const
+<lang-const>` keyword is preferred for defining constants.
+
+
+Syntax
+------
+
+The following line would define the name ``MY_CONSTANT`` to have value
+``value``::
+
+    #define MY_CONSTANT value
+
+Note that the ``#`` is necessary.  It is usually good style for the
+name to be capitalized, although this is not required.
+
+There is no semicolon after the #define statement. If you include one,
+the compiler will likely throw cryptic errors in unrelated places.
+That is, **don't do this**::
+
+    // DON'T DO THIS! THE SEMICOLON SHOULDN'T BE THERE!
+    #define NAME value;
+
+Similarly, including an equal sign after the ``#define`` line will
+also generate a cryptic compiler error further down the page.  That
+is, **don't do this, either**::
+
+    // DON'T DO THIS, EITHER! THE EQUALS SIGN SHOULDN'T BE THERE!
+    #define NAME = value
+
+Example
+-------
+
+::
+
+    #define LED_PIN 13
+    // The compiler will replace any mention of LED_PIN with
+    // the value 3 at compile time.
+
+See Also
+--------
+-  :ref:`const <lang-const>`
+
+
+.. include:: cc-attribution.txt