Bjarne Stroustrup mentions in his book "The C++ Programming Language, 4th Edition" that not all C++ implementations use files to store and compile code:
There are systems that do not store, compile, and present C++ programs
to the programmer as sets of files.
(Chapter 15, page 419)
Later in the chapter, he reiterates that certain implementations do not use files but he does not give any examples.
How would such an environment function compared to a more common file-based environment?