You're a little confused about how Visual Studio works with C++ files, but that's OK, since the documentation is lousy. First things first: unlike with C# or Java, the arrangement of files in the project has no relation to the arrangement of files on your disk. Files and folders aren't "in" the project, really; the project only lists the names and paths of the files and folders, which have to already exist on your disk.
In general, you create the layout of folders, with source files inside of those folders. You do this outside of Visual Studio. You also create a project file. When you "add a file" to the project, all you do is tell the project where to find the file on disk.
Let's work with a specific example and I'll show you how I would organize it. Suppose you are making a graphing calculator program called SuperCalc. You'll have a Source folder, and then create folders inside of Source to hold the different files. Suppose the folders you create are:
SuperCalcSourceInputSuperCalcSourceMathSuperCalcSourceMathMatrixSuperCalcSourceOutput
You have 3 subdirectories of Source: Input, Output, and Math. The Math subdirectory has a subdirectory called Matrix. You'll have .cpp files in Input, Math, Matrix, and Output. You'll create these directories (folders) using Windows Explorer or the Command Prompt.
Now you will also want to create a solution file (SuperCalc.sln) and a project file (SuperCalc.vcxproj & SuperCalc.vcxproj.filters). Do that inside of Visual Studio. Usually the project file lives in a sub-folder of the solution directory; this will be done automatically for you by Visual Studio. Pick a location for the
solution file -- it should be somewhere in the same directory structure (folder tree) as the source code. I would suggest putting it next to the Source directory, in:
Go into VS and pick File > New > Project > Visual Studio Solutions > Blank Solution File. Give the solution a name (maybe "SuperCalc") and a location (the location we just picked in the SuperCalcBuild directory). It will create the solution file for you.
Now right-click on the solution in the Solution Explorer ("Solution SuperCalc, 0 projects"), and pick Add > New Project. Pick a name -- this will be the name of your program executable, like "SuperCalc"! Choose Win32, either Win32 Console Application (this is a DOS-console program) or Win32 Project (this is an ordinary Windows GUI program). Usually I then click on Application Settings to make some important changes: for one thing, I pick Empty Project because I don't want Visual Studio creating files and code for me unless I tell it to. When it's all set up the way I want it, I click FINISH.
Now you've got your solution file and project, created by Visual Studio. You also have your source code, or at least the directory structure (folder tree) where your source code will be, created outside of Visual Studio. It's time to connect the two things together.
If you wanted, you could list all your source files into the Source Files filter of your project. Even though they will come from different directories (Input, Matrix, etc.), there's no required relationship between the locations of the files on disk and their appearance in the project. But if you have a lot of files, it is easier if you create "sub-filters", filters inside the Source Files filter, and give them the names of the sub-folders of Source. That way, you replicate the structure of your disk directories inside of your project file.
Right-click on the Source Files filter of the "SuperCalc" project, and pick Add > Add New Filter. Give it the name Input (the first of the SuperCalcSource directories). Also create the filters Math and Output. Right-click on the Math filter and pick Add > Add New Filter, to create a sub-filter called Matrix (inside of Math). Now you have these filters:
SuperCalc
Source Files
Input
Math
Matrix
Output
which parallels the directories (folders) you created earlier. This is purely a convenient arrangement for humans. Visual Studio doesn't understand anything special about it. If you just tell VS to "add a file" it won't put the file in the correct filter. You'll have to tell it where to put it.
To add or create your .cpp files, select the filter name corresponding to the directory where the .cpp file is. So, to add or create a file SuperCalcSourceMathMatrixmatrix_multiply.cpp, right-click on the Matrix filter in Solution Explorer, and pick Add > Add New File or Add Existing File. (Add Existing File is for when you have already written matrix_multiply.cpp and you just want to tell the project where it is.) Use the dialog box to navigate to the SourceMathMatrix directory. Repeat this process for all the source files in your whole program.
You also had the question "is there something similar to $(CURDIR) that I could use to include the source file folder without needing an absolute path?" You are in luck: Visual Studio projects don't use absolute paths! They use relative paths. The project file stores the relative path required to get from the directory containing the .vcxproj file to the directory containing the source file. So if you created SuperCalc.sln and SuperCalc.vcxproj where I suggested (the SuperCalcBuild directory), and you add your .cpp files in the source subdirectories, you can go look inside the SuperCalc.vcxproj file using Notepad, and you'll see lines like:
<ClCompile Include="......SourceMathMatrixmatrix_multiply.cpp" />
Since there are no absolute paths, you could take the entire SuperCalc directory tree and move it somewhere else, and it would all still work. No need for environment variable hacks like $(CURDIR).
One final thing to know: since you are putting your source files in multiple directories, you might have problems with #includeing headers, the .h or .hpp files. You must tell the compiler the directories where your header files are located. They will probably be scattered among multiple directories. So edit the project settings: right-click on the project name in Solution Explorer, choose Properties, and drill down to Configuration Properties > C/C++ > General. The first field in the property sheet says "Additional Include Directories". Before you do anything else, click on the Configuration drop-down menu and choose All Configurations. If you have both a 32-bit and 64-bit build, click on the Platform drop-down menu and choose All Platforms. Now go to the "Additional Include Directories" and add all the paths to all the source directories, with the paths specified relative to the project file's directory. So for the SuperCalc example, it would look like:
......SourceInput;......SourceMath;......SourceMathMatrix;......SourceOutput
Once this change is made, a file like SourceMathMatrixmatrix_multiply.cpp can have a
line
#include "input_configuration.hpp"
to #include a file from the Input directory, and it will All Just Work.
(If it doesn't All Just Work, the usual approach is to go back into Project Properties and fiddle with the number of .. sequences in front of your Additional Include Directories. Remember that every time you go to make a change you must choose All Configurations again -- otherwise your changes will only apply to the current Configuration (Debug or Release). That setting is not sticky.)
