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+.. highlight:: cpp
+
+.. _arduino-variables:
+
+Variables
+---------
+
+A variable is a way of naming and storing a value for later use by
+the program, such as data from a sensor or an intermediate value
+used in a calculation.
+
+
+
+Declaring Variables
+^^^^^^^^^^^^^^^^^^^
+
+Before they are used, all variables have to be declared. Declaring
+a variable means defining its type, and optionally, setting an
+initial value (initializing the variable). Variables do not have to
+be initialized (assigned a value) when they are declared, but it is
+often useful.
+
+
+
+::
+
+    int inputVariable1;
+    int inputVariable2 = 0;     // both are correct
+
+
+
+Programmers should consider the size of the numbers they wish to
+store in choosing variable types. Variables will
+`roll over <#VariableRollover>`_ when the value stored exceeds the
+space assigned to store it. See below for an example.
+
+
+
+Variable Scope
+^^^^^^^^^^^^^^
+
+Another important choice that programmers face is where to declare
+variables. The specific place that variables are declared
+influences how various functions in a program will *see* the
+variable. This is called variable
+`scope <http://arduino.cc/en/Reference/Scope>`_.
+
+
+
+Initializing Variables
+^^^^^^^^^^^^^^^^^^^^^^
+
+Variables may be *initialized* (assigned a starting value) when
+they are declared or not. It is always good programming practice
+however to double check that a variable has valid data in it,
+before it is accessed for some other purpose.
+
+
+
+Example:
+
+::
+
+     int calibrationVal = 17;  // declare calibrationVal and set initial value
+
+
+
+Variable Rollover
+^^^^^^^^^^^^^^^^^
+
+When variables are made to exceed their maximum capacity they "roll
+over" back to their minimum capacity, note that this happens in
+both directions.
+
+
+
+::
+
+       int x
+       x = -32,768;
+       x = x - 1;       // x now contains 32,767 - rolls over in neg. direction
+
+
+
+::
+
+       x = 32,767;
+       x = x + 1;       // x now contains -32,768 - rolls over
+
+
+
+Using Variables
+^^^^^^^^^^^^^^^
+
+Once variables have been declared, they are used by setting the
+variable equal to the value one wishes to store with the
+`assignment operator <http://arduino.cc/en/Reference/Assignment>`_
+(single equal sign). The assignment operator tells the program to
+put whatever is on the right side of the equal sign into the
+variable on the left side.
+
+
+
+::
+
+    inputVariable1 = 7;             // sets the variable named inputVariable1 to 7
+    inputVariable2 = analogRead(2); // sets the variable named inputVariable2 to the 
+                                    // (digitized) input voltage read from analog pin #2
+
+
+
+Examples
+^^^^^^^^
+
+::
+
+     int lightSensVal;
+       char currentLetter;
+       unsigned long speedOfLight = 186000UL;
+       char errorMessage = {"choose another option"}; // see string 
+
+
+
+Once a variable has been set (assigned a value), you can test its
+value to see if it meets certain conditions, or you can use its
+value directly. For instance, the following code tests whether the
+inputVariable2 is less than 100, then sets a delay based on
+inputVariable2 which is a minimum of 100:
+
+
+
+::
+
+    if (inputVariable2 < 100)
+    {
+      inputVariable2 = 100;
+    }
+    
+    delay(inputVariable2);
+
+
+
+This example shows all three useful operations with variables. It
+tests the variable ( ``if (inputVariable2 < 100)`` ), it sets the
+variable if it passes the test ( ``inputVariable2 = 100`` ), and it
+uses the value of the variable as an input parameter to the delay()
+function (``delay(inputVariable2)`` )
+
+
+
+**Style Note:** You should give your variables descriptive names,
+so as to make your code more readable. Variable names like
+**tiltSensor** or **pushButton** help you (and anyone else reading
+your code) understand what the variable represents. Variable names
+like **var** or **value**, on the other hand, do little to make
+your code readable.
+
+
+
+You can name a variable any word that is not already one of the
+`keywords <http://arduino.cc/en/Reference/Keywords?action=edit>`_`? <http://arduino.cc/en/Reference/Keywords?action=edit>`_
+in Arduino. Avoid beginning variable names with numeral
+characters.
+
+
+
+Some variable types
+^^^^^^^^^^^^^^^^^^^
+
+
+-  `char <http://arduino.cc/en/Reference/Char>`_
+-  `byte <http://arduino.cc/en/Reference/Byte>`_
+-  `int <http://arduino.cc/en/Reference/Int>`_
+-  `unsigned int <http://arduino.cc/en/Reference/UnsignedInt>`_
+-  `long <http://arduino.cc/en/Reference/Long>`_
+-  `unsigned long <http://arduino.cc/en/Reference/UnsignedLong>`_
+-  `float <http://arduino.cc/en/Reference/Float>`_
+-  `double <http://arduino.cc/en/Reference/Double>`_
+
+
+
+Variable Scope
+^^^^^^^^^^^^^^
+
+
+-  `Variable Scope <http://arduino.cc/en/Reference/scope>`_
+
+