They were meant for coding C on machines that had even less than ASCII as available text encoding really. So no wonder you never see them.

They were meant, mostly, for punch-card machines.

So if you started programming anywhere after the point in time when you needed to hand off your code to a punch card operator, you're unlikely to have seen them.

They were meant to support EBCDIC.

They're good for obfuscating source code but AFAICT that's about it on modern machines

Less obscure if physical print type head doesn't have the corresponding trigraph representation.

Unicode is a worthy successor to trigraphs -- no need for pre-processing!

Guess with tri-graph elimination & awk getting unicode support will have to gawk C with cpp using pipology theory.

But think the cpp has to go away first, after enough sed.

https://grayson.sh/blogs/using-piphilology-to-hide-strings

https://www.gnu.org/software/gawk/manual/gawk.html#Signature...