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.. highlight:: cpp
.. _lang-randomseed:
randomSeed()
============
``randomSeed()`` initializes the `pseudorandom number generator
<http://en.wikipedia.org/wiki/Pseudorandom_number_generator>`_,
causing it to start at an arbitrary point in its random sequence.
This sequence, while very long, and random, is always the same.
Library Documentation
---------------------
.. doxygenfunction:: randomSeed
Discussion
----------
If it is important for a sequence of values generated by
:ref:`random() <lang-random>` to differ, on subsequent executions of a
sketch, use ``randomSeed()`` to initialize the random number generator
with a fairly random input, such as :ref:`analogRead()
<lang-analogread>` on an unconnected pin.
Conversely, it can occasionally be useful to use pseudorandom
sequences that repeat exactly. This can be accomplished by calling
``randomSeed()`` with a fixed number, before starting the random
sequence.
Example
-------
The following sketch initializes the random seed based on an :ref:`ADC
<adc>` reading of pin 0. If this pin is unconnected, the Sketch
should print different values to the :ref:`serial monitor
<ide-serial-monitor>` each time it is run::
long randNumber;
void setup() {
pinMode(0, INPUT_ANALOG);
randomSeed(analogRead(0));
}
void loop() {
randNumber = random(300);
SerialUSB.println(randNumber);
delay(50);
}
See Also
--------
- :ref:`random() <lang-random>`
.. include:: /arduino-cc-attribution.txt
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