Main entities and output of First Level DFD (1st Level DFD): You will highlight the main functionalities of Library Management. DFD Level 1 provides a more detailed breakout of pieces of the 1st level DFD.
It also identifies internal data stores of Student, Employee, Publisher, Authors, Issue Book that must be present in order for the Library Management system to do its job, and shows the flow of data between the various parts of Library, Issue Book, Employee, Student, Publisher of the system.