c - random number generator

Question

How do I generate a random number between 0 and 1?

Answer 1

You can generate a pseudorandom number using stdlib.h. Simply include stdlib, then call

double random_number = rand() / (double)RAND_MAX;

Answer 2

Assuming OP wants either 0 or 1:

srand(time(NULL));
foo = rand() & 1;

Edit inspired by comment: Old rand() implementations had a flaw - lower-order bits had much shorter periods than higher-order bits so use of low-order bit for such implementations isn't good. If you know your rand() implementation suffers from this flaw, use high-order bit, like this:

foo = rand() >> (sizeof(int)*8-1)

assuming regular 8-bits-per-byte architectures