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<div class="title"><a href="http://www.arduino.cc"/>Arduino</a></div>
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<p><strong>Reference</strong> &nbsp; <a class='wikilink' href='index.html'>Language</a> (<a class='wikilink' href='Extended.html'>extended</a>) | <a class='wikilink' href='Libraries.html'>Libraries</a> | <a class='wikilink' href='Comparison.html'>Comparison</a>
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<p class='vspace'></p><h2>random()</h2>
<h4>Description</h4>
<p>The random function generates pseudo-random numbers.
</p>
<p class='vspace'></p><h4>Syntax</h4>
<p>long random(max)<br />long random(min, max)
</p>
<p class='vspace'></p><h4>Parameters</h4>
<p>min - lower bound of the random value, inclusive <em>(optional)</em>
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<p class='vspace'></p><p>max - upper bound of the random value, exclusive
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<p class='vspace'></p><h4>Returns</h4>
<p>long - a random number between min and max - 1
</p>
<p class='vspace'></p><h4>Note: </h4>
<p>If it is important for a sequence of values generated by random() to differ, on subsequent executions of a sketch, use randomSeed() to initialize the random number generator with a fairly random input, such as analogRead() on an unconnected pin.
</p>
<p class='vspace'></p><p>Conversely, it can occasionally be useful to use pseudo-random sequences that repeat exactly. This can be accomplished by calling randomSeed() with a fixed number, before starting the random sequence.
</p>
<p class='vspace'></p><h4>Example</h4>
<pre>
long randNumber;
void setup(){
Serial.begin(9600);
// if analog input pin 0 is unconnected, random analog
// noise will cause the call to randomSeed() to generate
// different seed numbers each time the sketch runs.
// randomSeed() will then shuffle the random function.
randomSeed(analogRead(0));
}
void loop() {
// print a random number from 0 to 299
randNumber = random(300);
Serial.println(randNumber);
// print a random number from 10 to 19
randNumber = random(10, 20);
Serial.println(randNumber);
delay(50);
}
</pre>
<p class='vspace'></p><h4>See also</h4>
<ul><li><a class='wikilink' href='RandomSeed.html'>randomSeed</a>
</li></ul><p class='vspace'></p><p><a class='wikilink' href='index.html'>Reference Home</a>
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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://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?board=swbugs' rel='nofollow'>Forum</a>.</em>
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<a class='urllink' href='http://creativecommons.org/licenses/by-sa/3.0/' rel='nofollow'>Creative Commons Attribution-ShareAlike 3.0 License</a>. Code samples in the reference are released into the public domain.
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