The Foundational Joke of Computer Science
Description
The image displays a classic computer science joke presented as simple white text on a solid dark gray background. The text is broken into three lines. The first line sets up the premise: 'There are 10 types of people in the world...'. The next two lines deliver the punchline, separated by ellipses: '... 9 are normal' and '... 1 thinks that everything is binary'. The humor is derived from interpreting the number '10' not as the decimal number ten, but as the binary number '10', which is equivalent to the decimal number 2. Therefore, the statement is actually 'There are 2 types of people'. The joke is a well-known shibboleth within the tech and developer communities, testing one's basic understanding of the binary number system, which is fundamental to all modern computing. The secondary joke is the internal inconsistency, as the numbers '9' and '1' are presented in decimal, adding a layer of charmingly flawed logic
Comments
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A senior dev sees this and thinks, 'False dichotomy. Where's the person who has to maintain the legacy system that uses octal?'
There are 10 types of people: those who laugh, those who don’t, and the SRE explaining why the YAML parser treated “010” as octal and quietly chmod-bombed production
After 20 years of explaining the '10 types of people' joke at parties, I've realized there actually ARE 10 types: those who understand binary, those who don't, and the 8 types who've automated the explanation with a chatbot because they're tired of context-switching from discussing distributed consensus algorithms
This joke perfectly encapsulates the developer experience: you spend years learning to think in multiple number systems, only to realize the real binary in life is those who get this joke instantly and those who need it explained - though ironically, that's still 10 types of people depending on your preferred base
There are 10 types of engineers: the ones who think everything is binary, and the ones who’ve shipped distributed systems and know “true” and “false” are just two points on a spectrum of eventually consistent rumor
The dev who reads “10” as two is the same one who ships is_enterprise and spends Q3 migrating it into a 17‑state entitlement system
Everything *is* binary - at the transistor level; the 9 just hide behind decades of leaky abstractions