It seems that Wikipedia refers to them as "Strings as records"[1], which I suppose fits quite well. I suppose that C strings could be considered "the most" cache friendly since it has only 1 byte overhead instead of however many bytes would be required for the length (probably 4 or 8 bytes on most modern systems). That said, I would be extremely surprised for this difference of a few bytes per string to have a measurable performance improvement in anything but an unrealistic microbenchmark involving many tiny strings.

1: https://en.wikipedia.org/wiki/String_(computer_science)#Stri...