For my BSc work I wrote a (rather clumsy) quadratic sieve implementation. This was my first larger programming project and required me to transfer my understanding of Visual Basic for Applications, PHP and C# to C++ while also using a large number library.
In retrospect many aspects of the code can almost certainly be improved, however at the time it was what I wrote - trying to follow a step by step structure in applying the quadratic sieve to a number that needs to be factorized.
The source as well as the executable can be found on sourceforge and require the .net Framework from Microsoft to run.
I might update the code at some point when I have the time, however this should not be expected given that I am busy with other work.
The project is provided "as is" with all its flaws and limitations.