======random()   ======

====Description   ====
The random function generates pseudo-random numbers. 

====Syntax   ====
random(max)\\
random(min, max)

====Parameters   ====
min - lower bound of the random value, inclusive  ''(optional)''

max - upper bound of the random value, exclusive

====Returns   ====
a random number between min and max-1 (''long'')

====Note:    ====
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.

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.

====Example   ====

<code arduino>
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);
}
</code>

====See also   ====
* [[arduino:random numbers:RandomSeed]]


Source: arduino.cc