−1 This does not reply the query from the title, “When is #include things like library expected in C++?”. I assume that that might be Alright Using the OP. But it's dilemma when this query is made use of as referent for the close-as-copy of some other query. @Oriol https://phase2directory.com/listings13454330/how-sabrina-carpenter-espresso-cover-song-can-save-you-time-stress-and-money