Creating a random array of Bits

Question

Using rand(), I'm trying to create an array which generates 32 random numbers each time I run the program. However my program below gives me the same 32 random bits each time. Is there anyway I can get it to generate different 32 bits each time I run the program?

    for(a=0;a<32;a++)
    {
        ran[a]= (rand()%2);
    }

Wouldnt rand() be already 16 distinct -randomed-bits, did you try expanding it to 16 bits ? This is 16 times faster. — huseyin tugrul buyukisik, Apr 09 '15 at 17:02
`srand(time(NULL));` before your loop will seed the pseudo-random-number generator with the time in seconds. As long as you don't run your program twice in the same second, you'll get new numbers. — DoxyLover, Apr 09 '15 at 17:04
Even when properly seeded, rand() is terrible in the low-order bits, and your `%2` is throwing away all but the lowest-order bit. After fixing the seed, then change your `r%2` to `(r>>4)&1`. — Lee Daniel Crocker, Apr 09 '15 at 17:40

score 0 · Answer 1 · answered Apr 09 '15 at 17:04

You need to set up the random seed each time you run the program to something different to do that. What people do is usually this:

#include <time.h>       /* time */
...
srand (time(NULL));
... 
//Calls to rand();

Then your random seed is different at every start of the program. Check more details about srand here.

Creating a random array of Bits

1 Answers1