What‘s the difference between srand(1) and srand(0)

Question

I just found out the hard way that srand(1) resets the PRNG of C(++) to the state before any call to srand (as defined in the reference). However,

Answer 1

Neither the C nor the C++ standards say much about the specifics of the implementation of rand() and srand(). The details are left almost entirely up to the implementor. The C standard requires that:

If srand is then called with the same seed value, the sequence of pseudo-random numbers shall be repeated. If rand is called before any calls to srand have been made, the same sequence shall be generated as when srand is first called with a seed value of 1.

but it does not contain any requirement that different seeds must produce different sequences. Apparently, on your system, seeds of zero and one have the same effect. I would guess that this is to provide backwards compatibility with some piece of software that expects srand(0) to reset the PRNG to its initial state.