For context, the original joke is:

> There are 10 kinds of people in this world — those who understand binary and those who don’t.

There are other versions too[1][2][3].

[1]: https://news.ycombinator.com/item?id=7036594

[2]: https://news.ycombinator.com/item?id=7040175

[3]: https://news.ycombinator.com/item?id=25854900