random()

Description

The random function generates pseudo-random numbers.

Syntax

Use the following function to generate a random number:

• random(max)

• random(min, max)

Parameters

The function admits the following parameters:

• min

  : lower bound of the random value, inclusive (optional)

• max

  : upper bound of the random value, exclusive

Returns

The function returns a random number between min and max-1. Data type:

long

Example Code

The code generates random numbers using the different variants of the function and prints them in the Serial Monitor.

1long randNumber;
2
3void setup() {
4  Serial.begin(9600);
5
6  // if analog input pin 0 is unconnected, random analog
7  // noise will cause the call to randomSeed() to generate
8  // different seed numbers each time the sketch runs.
9  // randomSeed() will then shuffle the random function.
10  randomSeed(analogRead(0));
11}
12
13void loop() {
14  // print a random number from 0 to 299
15  randNumber = random(300);
16  Serial.println(randNumber);
17
18  // print a random number from 10 to 19
19  randNumber = random(10, 20);
20  Serial.println(randNumber);
21
22  delay(50);
23}

Notes and Warnings

If it is important for a sequence of values generated by

random()

randomSeed()

analogRead()

Conversely, it can occasionally be useful to use pseudo-random sequences that repeat exactly. This can be accomplished by calling

randomSeed()

The

max

long

max

See also

• randomSeed()