I gave a talk called "What is a Random number and why should I care?" a few times last year. It evolved each time, but I was fundamentally trying to decide whether I could define "randomness" properly.

My first attempt was at ACCU. Unfortunately, in a surprising turn of events, my laptop died, but I did manage to give the talk using a pdf version on someone else's laptop. I got other chances at other conferences, for example MeetingCpp, so you can watch if you are interested.

The second part of my title - why should I care - is easier to answer than the first. Without randomness, however we define this, outcomes are predictable, which is boring. For example, letting some blobs march up the screen at the same pace gives a very predictable outcome:

*a random number*, but

*a sequence of numbers might be random*. If you can predict what comes next the numbers are not random, but if you can't that proves nothing. For example, what digit comes next in this sequence?

*multiplicative linear congruential generator*

_{i+1}=Ax

_{i}modM

*stochastic*or (psuedo) random functions, and my latest book, Learn C++ by Example, aimed at helping people get back up to speed with C++, also has several simple games, like a higher/lower card game. To make the games fun, you get lots of practice using C++'s random numbers. The C++ book is currently on pre-order at Amazon, or you can buy it directly from the publishers.

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