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    <p>I'm pretty sure YOU are supposed to create the ArrayIntStorage.h header AND implement the matching ArrayIntStorage.cpp.</p> <p>Based on the "// sort data structure using std" comment you are expected to use and create a wrapper over an appropriate stl container, something like std::vector.</p> <p>Based on the "// do not read sort" comment, you should, by default, sort the vector after each insert (unless, of course, someone calls setReadSort(false) on your wrapper).</p> <p>In addition to the interface described above, you still need to implement >> and &lt;&lt;.</p> <p>UPDATE.</p> <p>Reading you question at <a href="https://stackoverflow.com/questions/5842583/c-pass-variable-from-cpp-to-header-file">C++ pass variable from .cpp to header file</a> you seem to be quite confused by all this...</p> <p>First thing first, adding support for >> and &lt;&lt; operators:</p> <p>You do this by declaring these operators in your .h file:</p> <pre><code>friend std::ostream&amp; operator&lt;&lt;(std::ostream &amp;out, const ArrayIntStorage &amp;a); friend std::ifstream &amp; operator&gt;&gt;(std::ifstream &amp;, ArrayIntStorage &amp;); </code></pre> <p>You then define their implementation in the .cpp file:</p> <pre><code>std::ostream&amp; operator&lt;&lt;(std::ostream &amp;out, const ArrayIntStorage &amp;a) { return out; } std::ifstream &amp; operator&gt;&gt;(std::ifstream &amp;, ArrayIntStorage &amp;) { return in; } </code></pre> <p>Obviously, you need to add some proper code there, this is just to make it compile. If it still doesn't compile, check if you have included the stream headers in your .h file:</p> <pre><code>#include &lt;fstream&gt; #include &lt;iostream&gt; </code></pre> <p>Now for some general info:</p> <p>Your array storage should be based on something like std::vector. The purpose of the >> and &lt;&lt; function you need to implement is to add and retrieve int's from that container. </p> <p>Since the ArrayIntStorage is a class, once you've established the interface you need ( the public member functions in the .h file) you should only look at the .h and .cpp to flesh out the implementation.</p> <p>Once that is done, you don't need any of the "extern" madness the answers to your other question said. Look at your main function. If creates an object of your class and the fin1 stream. It then calls the >> operator you've implemented. All of this is done with local variables.</p> <p>This is how you "use the value of this variable from main.cpp". You call a member function of your class with that variable as a parameter.</p> <p>And finally, if you have all these problems with understanding header files and link errors, are you sure you've started with the proper training exercise?</p>
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    1. COi know i have to create the header file, but i haven't heard anything about creating a matching cpp file. As for your last point i do get errors when i have made the header file about the << and >> operators. i tried to get round it with this line `std::ostream& operator<<(ostream &out, const ArrayIntStorage &a)` and a similar one line for >>. these gave me "LNK" linker errors in my header file
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    2. COthank you! i have now done a few other exercises and understand it more.
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