Understanding the algorithm of Visual C++'s rand() function

Question

In C/C++, rand() and srand() are usually used by us when we want to get a random integer. But when I tried to rewrite it myself, I found it difficu

Answer 1

It's just modular arithmetic. You're multiplying and adding to a number which is taken modulo 2^32 (for example), and returning the upper 16 bit as your "random" number. Because you're multiplying and adding numbers which are coprime to the modulus, this creates sort of uniformly distributed numbers.

The careful choice of the two numbers is very important. For example, if you had used "* 4" and "+ 8", you would probably not experience a lot of randomness.

This scheme is called linear congruential.