What does the C??? operator do?

C++17 will deprecate trigraphs, but interestingly they still are a thing in mainframe space. Here are two (PDF) documents from IBM about it:<p><a href="http:&#x2F;&#x2F;www.open-std.org&#x2F;jtc1&#x2F;sc22&#x2F;wg21&#x2F;docs&#x2F;papers&#x2F;2014&#x2F;n4210.pdf" rel="nofollow">http:&#x2F;&#x2F;www.open-std.org&#x2F;jtc1&#x2F;sc22&#x2F;wg21&#x2F;docs&#x2F;papers&#x2F;2014&#x2F;n421...</a><p><a href="http:&#x2F;&#x2F;www.open-std.org&#x2F;jtc1&#x2F;sc22&#x2F;wg21&#x2F;docs&#x2F;papers&#x2F;2009&#x2F;n2910.pdf" rel="nofollow">http:&#x2F;&#x2F;www.open-std.org&#x2F;jtc1&#x2F;sc22&#x2F;wg21&#x2F;docs&#x2F;papers&#x2F;2009&#x2F;n291...</a>

I&#x27;ve never seen them around. Even my dad who was a programmer during the 90&#x27;s says so.

For those that are wondering, its a trigraph sequence! No one uses them anymore.