Introduction - If you have any usage issues, please Google them yourself
Program main menu contains the following features:
(1) add records: through the keyboard input information, add a directory records.
(2) delete records: through the keyboard input student id and delete this student id records.
(3) output records: output contacts all records.
(4) by name lookup: through the keyboard input, output this classmate name all the information.
Keep the records (5) : all directories records in a file.
(6) : delete the directory of empty records all records, and deleting files.
(7) from