How to combine several file streams to one memory binary stream?

ostream is an abstract base class - that's why you can't instantiate it. Also, you can't use the insertion operator on streams to get what you're wanting.

So...what do you mean by "memory binary stream"? If you were using strings, then this should work:

ifstream ifs1("file1");<br />ifstream ifs2("file2");<br />ostringstream oss;<br />std::copy(std::istream_iterator<char>(ifs1), std::istream_iterator<char>(), std::ostream_iterator<char>(oss));<br />std::copy(std::istream_iterator<char>(ifs2), std::istream_iterator<char>(), std::ostream_iterator<char>(oss));