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diff --git a/source/arduino/variables.rst b/source/arduino/variables.rst deleted file mode 100644 index 0720041..0000000 --- a/source/arduino/variables.rst +++ /dev/null @@ -1,191 +0,0 @@ -.. 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. - -.. _arduino-variables-declaring: - -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. - -.. _arduino-variables-scope: - -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>`_. - -.. _arduino-variables-initializing: - -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 - -.. _arduino-variables-rollover: - -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>`_ - - - - -.. include:: cc-attribution.txt |