Question

I would like to go through how rand() and srand() functions are implemented and would like to tweak the code to modify it to my requirements. Where can i find the source code of rand() and srand().

Answer 1

It takes a seed as in input argument, usually like follows:-

double result = srand(time(NULL));

and returns a random number that adheres to the probability and hence expected number of occurrences.

from CodeGuru forums:-

void __cdecl srand (unsigned int seed)
{
    #ifdef _MT
        _getptd()->_holdrand = (unsigned long)seed;
    #else /* _MT */
        holdrand = (long)seed;
    #endif /* _MT */
}

int __cdecl rand (void)
{
   #ifdef _MT
    _ptiddata ptd = _getptd();
    return( ((ptd->_holdrand = ptd->_holdrand * 214013L + 2531011L) >> 16) &
    0x7fff );
   #else /* _MT */
    return(((holdrand = holdrand * 214013L + 2531011L) >> 16) & 0x7fff);
   #endif /* _MT */
}

Hope this helps.