C rand() function

C rand() function - Pseudo-random number generator

The rand() function is used to compute a sequence of pseudo-random integers in the range [0, {RAND_MAX}]. The value of the {RAND_MAX} macro shall be at least 32767.

Syntax rand() function

int rand(void)

Parameters rand() function

NA

Return value from rand()

• Returns a pseudo-random number.

Example: rand() function

The following example shows the usage of rand() function.

#include <stdlib.h>
#include <stdio.h>
 
int main(void)
{
   int n;
 
   for (n = 1;n <= 12; n++)
      printf("iteration %d, rand = %d\n", n, rand());
}

Output:

iteration 1, rand = 41
iteration 2, rand = 18467
iteration 3, rand = 6334
iteration 4, rand = 26500
iteration 5, rand = 19169
iteration 6, rand = 15724
iteration 7, rand = 11478
iteration 8, rand = 29358
iteration 9, rand = 26962
iteration 10, rand = 24464
iteration 11, rand = 5705
iteration 12, rand = 28145

The following example shows the usage of rand() function.

#include <stdlib.h>
#include <stdio.h>
 
int main(void)
{
   int range_min = -100;
   int range_max = 100;
   int n = 100000;
 
 for (int i = 0; i < n; i++)
    {
        // Note: This method of generating random numbers in a range isn't suitable for
        // applications that require high quality random numbers.
        // rand() has a small output range [0,32767], making it unsuitable for
        // generating random numbers across a large range using the code below.
        // The approach below also may result in a non-uniform distribution.
        // More robust random number functionality is available in the C++ <random> header.
        int r = ((double)rand() / RAND_MAX) * (range_max - range_min) + range_min;
        printf("  %6d\n", r);
    }
}

Output:

 ...
 ...
 59
 76
  8
-12
 64
 82
-93
 32
 62
 37
-51
-74
-93
-10
 72
-88
 -7
 68
 45
-85
-38
...
...
...
...

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