Those who understand binary, and those who don’t.
In my early days as a computer programmer, I studied the RCA 501, a 2nd generation computer (in the days of vaccuum tubes, before transistors). It was an octal machine. If you ever saw any of the original Startrek TV series, the console of the Starship Enterprise was actually the console of an RCA 501. Its console made for a very dramatic display, and it was for real (although I’m not aware of any 501 actually going into space!).
Our programs were keypunched into paper tape, which was fed into the machine. There was a primitive Operating System, but that did not include error handling. If the computer read a bad instruction or otherwise hung up, it would come to a halt (which was the purpose of the lighted console — to be able to read the location of the stop and what was in all the registers).
When the machine hung, the operator called the programmer to come to the computer room. Our job at that point was to figure out how to write memory to get the machine going again. Then, a patch (literally) needed to be made to the paper tape so the same thing wouldn’t happen again. We coded up the correction, had it keypunched, and in order to fix the tape, we had to hold it up to the light and read the instructions so we would know where to cut out the offending code and insert the new strip of paper tape. So I got pretty good at reading octal (which is base 8 — three binary digits strung together).
I like the joke about 10 types of people. Hadn’t heard that one before.