# Random number

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Generating **random numbers** is a task that comes up a lot while programming. It is often important to know how to do it properly as a lot of languages generate **pseudorandom numbers** by default.

"Real" random numbers are numbers that are generated with statistical randomness, in contrast to pseudorandom numbers which are generated by using a seed. Supplying the same seed to a pseudorandom number generator would yield the same numbers. In most programming languages, the seed is set to the system's time by default; this will create the illusion of generating statistically random numbers.

## Examples Edit

### C Edit

srand(time(0)); int num = rand() % 10; // generates a number from 0 to 9

### .NET Edit

The System.Random class is used to generate random numbers. Each instance is a separate pseudorandom number generator.

#### C# Edit

Random random = new Random(); random.Next(); random.Next(10); // generates a number from 0 to 9

#### Visual Basic Edit

Dim rand As New Random() rand.Next(10)

### Java Edit

Random rand = new Random(System.currentTimeMillis()); //seeding Random with current time // Random integers int i = rand.nextInt(); int j = rand.nextInt(10); // generates a number from 0 to 9

**See Also**

### Perl Edit

int(rand(10)) # generates a number from 0 to 9

### PHP Edit

rand(0, 9) // generates a number from 0 to 9 mt_rand(0, 9) // like above, but use the MT method

### PL/I Edit

dcl time builtin; /* System time HHMISS999 */ dcl random builtin; dcl number bin fixed(15); number = random(time()) * 100 + 1; /* Range 1 - 100 */

### Python Edit

import random print random.random() print random.randrange(10) # generates a number from 0 to 9 print random.randint(0, 9) # generates a number from 0 to 9

### Ruby Edit

rand(10) # generates a number from 0 to 9

### Ada Edit

declare type Rand_Range is range 0..9; package Rand_Int is new Ada.Numerics.Discrete_Random(Rand_Range); seed : Rand_Int.Generator; Num : Rand_Range; begin Rand_Int.Reset(seed); Num := Rand_Int.Random(seed); Put_Line(Rand_Range'Image(Num)); end;