What projects can I build around semester 3 during an MCA?

A strong MCA project should solve a clear problem and demonstrate real technical work. A student can strengthen it with proper documentation, testing, source control and a working demonstration. The practical value of semester 3 becomes clearer when you use it to solve an actual problem instead of studying definitions alone. This point is specifically relevant to the semester 3 aspect of MCA study. For this specific question about semester 3, the practical takeaway is to relate the concept to your own MCA learning goal.