3. APPICATION CONTROLLER: provides stable, consistent way for applications to deal with hardware without knowing of its detail.

6. It takes care of illegal instructions or commands, reports error accordingly.

8. It transfers main memory contents in specific filenames, to discs and vice versa.

11. OS partitions memory for different users and programs.

13. It also maintains a log and keeps track of login and logout of particular users, commands entered by user, files used, and jobs carried out.