I came across this a week ago when I was looking at some LLM generated code for a ToUpper() function. At some point I “knew” this relationship, but I didn’t really “grok” it until I read a function that converted lowercase ascii to uppercase by using a bitwise XOR with 0x20.

It makes sense, but it didn’t really hit me until recently. Now, I’m wondering what other hidden cleverness is there that used to be common knowledge, but is now lost in the abstractions.