Introduction - If you have any usage issues, please Google them yourself
In actual applications tend to use a pseudorandom number is sufficient. The number of columns is " as if" a random number, in fact they are through a fixed, repeatable calculation produced. A random number generated by a computer or a calculator has a long periodicity. They are not really random, because they can actually be calculated, but they have similar statistical characteristics of random numbers. Such a pseudo random number generator is called the generator. In the real critical applications, such as in cryptography, people generally use a truly random number.