|
rand
int rand ( void ); | stdlib.h |
| cplusplus.com |
Generate random number.
Returns a pseudo-random number in the range from 0 to RAND_MAX
constant. This is generated by an algorithm that returns a series
of non-related numbers each time is called. This algorithm should be initialized
to different starting points using function
srand to generate more realistic random numbers.
RAND_MAX is a constant defined in stdlib.h. Its default value is
implementation defined.
Parameters.
Return Value.
An integer value between 0 and RAND_MAX.
Portability.
Defined in ANSI-C.
Example.
/* rand example */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
main ()
{
/* initialize random generator */
srand ( time(NULL) );
/* generate some random numbers */
printf ("A number between 0 and RAND_MAX (%d): %d\n", RAND_MAX, rand());
printf ("A number between 0 and 100: %d\n", rand()%100);
printf ("A number between 20 and 30: %d\n", rand()%10+20);
return 0;
}
A good way to generate true random numbers is to initialize the random algorithm
using srand with the current time in seconds as parameter
obtained from time function included in <time.h>.
See also.
srand