Rand Implementation

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rand and srand are usually implemented as a simple LCG, you can easily write your own (it’s few lines of code) without looking for the sources of rand and srand. Notice that, if you need random numbers for “serious” purposes (e.g. cryptography), there are much better RNGs than LCG.

By the way, the C standard itself includes a sample implementation of rand and srand:

static unsigned long int next = 1;

int rand(void) // RAND_MAX assumed to be 32767
{
    next = next * 1103515245 + 12345;
    return (unsigned int)(next/65536) % 32768;
}

void srand(unsigned int seed)
{
    next = seed;
}

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