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<p class='vspace'></p><h2>Variable Scope</h2>
<p>Variables in the C programming language, which Arduino uses, have a property called <em>scope</em>. This is in contrast to languages such as BASIC where every variable is a <em>global</em> variable.
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<p class='vspace'></p><p>A global variable is one that can be <em>seen</em> by every function in a program. Local variables are only visible to the function in which they are declared. In the Arduino environment, any variable declared outside of a function (e.g. setup(), loop(), etc. ), is a global variable.
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<p class='vspace'></p><p>When programs start to get larger and more complex, local variables are a useful way to insure that only one function has access to its own variables. This prevents programming errors when one function inadvertently modifies variables used by another function.
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<p class='vspace'></p><p>It is also sometimes handy to declare and initialize a variable inside a <em>for</em> loop. This creates a variable that can only be accessed from inside the for-loop brackets.
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<p class='vspace'></p><h4>Example:</h4>
<pre>int gPWMval; // any function will see this variable
void setup()
{
// ...
}
void loop()
{
int i; // "i" is only "visible" inside of "loop"
float f; // "f" is only "visible" inside of "loop"
// ...
for (int j = 0; j <100; j++){
// variable j can only be accessed inside the for-loop brackets
}
}
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<p class='vspace'></p><p><em>Corrections, suggestions, and new documentation should be posted to the <a class='urllink' href='http://arduino.cc/forum/index.php/board,23.0.html' rel='nofollow'>Forum</a>.</em>
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