Rfid Library

hi
I am in 4 grade computer department
and my final project is about (rfid library)
the component of project is
1 / reader
2 / tag
3 / data base

i used a pic16f877a in reader to read tags from books
and save the id for each tag in the memory

and then connect reader to pc through usb

and transfer data to data base

i want to know what exactly happened when i connect reader to pc

can anyone tell me the sequence

and i want to make flow chart for what happening

thx​