Adds a simple readme

code_students/README.md

+## Code
+
+The code is written in C++ and requires C++17 and `cmake` to build.
+Additionally, we require hdf5 used for writing data to disk.
+The project is a simple finite-volume hydrodynamics code with second-order spatial reconstruction and second-order time-integration.
+It uses a semi-discrete version of the finite-volume scheme with an HLL Riemann solver.
+
+### Prerequesites
+
+The code requires hdf5, which should be available via your software environment.
+Additionally, it uses Googletests.
+This can be cloned from `git@github.com:google/googletest.git`.
+Copy this into a directory of your choice, then go to the main directory, created a directory `build` and in this directory execute
+
+    cmake .. -DBUILD_GMOCK=OFF -DCMAKE_INSTALL_PREFIX=/your/install/path
+
+where you need to specify the install path.
+Finally, build the code via `make install`
+
+### Directory structure.
+
+The project uses `cmake` to build.
+You can find the file `CMakeLists.txt` in the code's main directory.
+Header files can be found in `include` and its subdirectories.
+Similarly, `src` and it's sub directories hold the source files.
+Additionally, `apps` contains all source files holding `main` functions, thus allowing different setups of the code.
+That also means, you can create a new setup, by copying one of the source files in `apps` and extending the `CMakeLists.txt` in the same directory correspondingly.
+
+### Building the code
+
+You can build the code by creating a build-directory, e.g., via `mkdir build`.
+Next, change into that directory, execute `cmake ..` and `make install`.
+This will install the executables in the directory `bin` in the main code directory.