Pedantic: What Is A Source File? What Is A Header?

Question

For the purposes of this question, I am interested only in Standard-Compliant C++, not C or C++0x, and not any implementation-specific details.

Questions arise from

Answer 1

My reading is that the standard headers, included by use of <> angle brackets, need not be actual files on the filesystem; e.g. an implementation would be free to enable a set of "built-in" operations providing the functionality of iostream when it sees #include .

On the other hand, "source files" included with #include "xxx.h" are intended to be literal files residing on the filesystem, searched in some implementation-dependent manner.

Edit: to answer your specific question, I believe that "headers" are limited only to those #includeable facilities specified in the standard: iostream, vector and friends---or by the implementation as extensions to the standard. "Source files" would be any non-standard facilities (as .h files, etc.) the programmer may write or use.