There used to be a saying: Computer science is no more about computers than astronomy is about telescopes.
And that is why in this article, ESR has titled it, Things Every _Hacker_ Once Knew. Hackers usually have some sort of passion for the technology itself and want to understand ALL of the practical details and history of a thing. Hackers are _very much_ about computers.
This one is a bit confusing. In DOS/Windows land, files are just files, always binary. The distinction between "ASCII" and "Binary" only exists at the time you call "fopen" (a C function), then failing to open in binary mode causes it to mangle your data by inserting CR before every LF.
I meant text files vs. binary files, as in, you can open text files in a text editor and see their contents, but if you open a binary file in a text editor, you get what appears to be garbage, but that is not an error, because of all the non-printable characters they often contain.
But at one level you are right, of course, files are just files. It is the higher layers of software and humans that give different interpretations to them, such as text vs binary.
>talked, voice-to-text error
hex
octal
binary
how to convert between the above 3, and between them and decimal
bit twiddling
the difference between ASCII and binary files (even pre-unicode)
the fact that a source code program compiled on one processor architecture will not run on another without recompilation on the target, apart from cross-compilation - at least in most cases this was true, though there might be differences nowadays, for apple products, java and other bytecode, etc.
endianness
...
I have actually talk to various people who did not know all of the above topics, although not necessarily all in the same person