Re: rand and srand

Bill Cunningham wrote:
I am stumped on this one. I tried two methods and something just doesn't seem right. I'll try my new syle.

#include <stdio.h>
#include <stdlib.h>

main() {
srand(2000); /*seed unsigned */
printf("%u",rand());
}

Now I get a number much larger than 2000. Also when I also try RAND_MAX with srand from time to time.

With main I was always told int was the default type and didn't need to be declared. Main() has always worked. I hope this code is much more readable.

Bill



The function rand() returns a value between 0 and RAND_MAX, not between 0 and what you pass to srand(). The latter function only sets the seed for the random number generator (on which the next random number will be based).

If you want to have a non-predictable sequence of random numbers, it's often a good idea to set the seed to something that is not a literal and will change each time the program is executed.

Additionally, if you want to generate a random number between 0 and 2000, the code to do that uses the modulus operator, thusly:

printf("%u\n", (rand() % 2001));

For one, without the \n (newline), nothing will separate your numbers from each other. The second part of this is the % 2001. That divides the value from rand() by 2001, and returns the remainder - so the number can be anything from 0 to 2000. If rand() returns 2001, the modulus makes it 0, etc.

As for your main(), I wasn't actually aware that such code was legal C. My guess is that it is actually void main(), because you never return a value from it, so the exit status of your program is most likely undefined. It is a good idea, particularly in UNIX, to declare it int, and return 0 at the end (unless the program failed).

--
--Falcon Kirtaran
.

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