为什么c++ stdlib rand()函数在不同的平台上为相同的种子提供不同的值?

I understand that the rand() function generates pseudo-random numbers based on the seed it is given, and that on a given platform it will always generate the same sequence of numbers from the same seed, what I want to know is why it gives a different sequence across platforms that use the same library? I.e. how is function generates