Thread: Random Integer

Code:

srand(time(NULL));

That's how you seed the random number generator. Because the time is somewhat random, you get a different starting-point for the random number generator every time you run your program.

If your program has a loop, make sure you seed only once outside the loop. If the loop runs fast, it can be re-seeded with the same time, and you'll get the same "random" number more than once.

[EDIT]
This is from cppreference.com

time
Syntax:
#include <time.h>
time_t time( time_t *time );

The function time() returns the current time, or -1 if there is an error. If the argument time is given, then the current time is stored in time.


srand
Syntax:
#include <stdlib.h>
void srand( unsigned seed );

The function srand() is used to seed the random sequence generated by rand(). For any given seed, rand() will generate a specific "random" sequence over and over again.

srand( time(NULL) );
for( i = 0; i < 10; i++ )
printf( "Random number #%d: %d\n", i, rand() );