Write a C++ program with the following functionalities: -

Note: Make this program using concepts of data structures. It should be a modular programming based solution. You have to use data structures like queues, stacks, trees, graphs to make this program.

1. To add, delete, search and update records of a student.

2. Save the records of student in a .txt file. The records can be student name, address, city name, father name, department name etc.

3. A function that tells which department of the school has the most students.

The code for this program must be divided as separate (.h, .cpp) files.