"one-to-one correspondence with files in a file system"

Question

I have read in the c# language specification :

Source files typically have a one-to-one correspondence with files in a file system, but this correspondence is not required

What does this exactly mean ?

Answer 1

As the line before it says:

A source file is an ordered sequence of Unicode characters

That means a "source file" doesn't necessarily have to be a file on the file system. It could be any old stream of bytes that represent characters in UTF-16. It could come from a memory stream, or from a network, or from any old place. But usually it's a file on the file system.