rand
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Generates a pseudorandom number. A more secure version of this function is available, see rand_s.
Syntax
int rand( void );
Return Value
rand returns a pseudorandom number, as described above. There is no error return.
Remarks
The rand function returns a pseudorandom integer in the range 0 to RAND_MAX (32767). Use the srand function to seed the pseudorandom-number generator before calling rand.
Requirements
| Routine | Required header |
|---|---|
rand |
<stdlib.h> |
For additional compatibility information, see Compatibility in the Introduction.
Example
// crt_rand.c
// This program seeds the random-number generator
// with the time, then exercises the rand function.
//
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
void SimpleRandDemo( int n )
{
// Print n random numbers.
int i;
for( i = 0; i < n; i++ )
printf( " %6d\n", rand() );
}
void RangedRandDemo( int range_min, int range_max, int n )
{
// Generate random numbers in the half-closed interval
// [range_min, range_max). In other words,
// range_min <= random number < range_max
int i;
for ( i = 0; i < n; i++ )
{
int u = (double)rand() / (RAND_MAX + 1) * (range_max - range_min)
+ range_min;
printf( " %6d\n", u);
}
}
int main( void )
{
// Seed the random-number generator with the current time so that
// the numbers will be different every time we run.
srand( (unsigned)time( NULL ) );
SimpleRandDemo( 10 );
printf("\n");
RangedRandDemo( -100, 100, 10 );
}
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27464
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3284
11785
14686
11447
11285
74
48
27
65
96
64
-5
-42
-55
66