Comment by somat
Yeah that sucks, the hard life lesson where you have to swallow your pride and go "fine, I will put quotes on the infernal thing"
But... it does not print a string, a string goes into it but what comes out of the function is not that programmatic feature we call a string in any way shape or form, what comes out depends on the output device specified, it may be ink on paper, lit phosphors, or a stream of bytes. none of which can you use in your program as a string.
sprintf being a notable exception of course. there you do get a string out of it.
Update: language is weird and the more I read my statement the weirder it gets, all I can do is add this cryptic note. "When you print a string it does not produce a string", this usually means I am wrong about something.
"string" is a type that only makes sense inside the context of a specific programming language, because programming languages differ on what a string is and how it behaves (is it guaranteed to be valid UTF8, does it carry its own length around with it, is it runes/graphemes and can't be split on byte boundaries easily, is it mutable, etc).
Double quotes are a syntax sugar for string literals in source code, in a particular language, to avoid writing `string.from_byte_array([97, 98, 99])` or `new String({97, 98, 99});` or whatever. Strings are single quoted not double quoted in Dyalog APL, there's several different strings in SWI Prolog depending on using double quotes or backticks and how the flags are set.
stdout is an untyped byte stream which could go to a printer or Braille terminal or anything as you say, but could be terminal control codes, image data, or whatever. The OS doesn't tend to have a 'string type' ... but in PowerShell `write-output "a"` will write a .NET System.String to the output stream, but it won't use "printf()".