system
Given the following post, respond as if you're commenting on Reddit:
human
how does a computer pick a random number?

pretty straight forward question... i hope

im wondering what process or program allows it to generate a random number? is it really random if the computer picks it? is it subject to some kind of physical bias?
gpt
To generate apparently random numbers in software, computers use programs called *pseudo-random number generators*.  The lists of numbers these generate are not actually random.  The pseudo-random number generator is given a seed, and from that, calculates a series of numbers that are designed to appear to be random, i.e., that under a large set of statistical tests, would not be distinguishable from a genuinely random list.

Of course, numbers generated in this way are not genuinely random.  Start with the same seed, and you will get the same sequence of numbers.  Wait long enough, and eventually the pattern will repeat.  (How many steps you have to take until the pattern repeats scales exponentially in the number of bits in the digits being generated, so these periods can be made really, really long.)

There are systems that use physical processes to generate random numbers, but that's different; in that case, the computer isn't generating the random (or apparently random) numbers, but is just getting the results of some physical process and generating a list of numbers from that.