One set of operating-system services provides functions that are helpful to the user:
User interface .............................- Almost all operating systems have a user interface (UI)
Varies between Command-Line (CLI), Graphics User Interface (GUI), Batch
Program execution .....................- The system must be able to load a program into memory and to run that program, end execution, either normally or abnormally (indicating error)
I/O operations......................... - A running program may require I/O, which may involve a file or an I/O device.
File-system manipulation ......................- The file system is of particular interest. Obviously, programs need to read and write files and directories, create and delete them, search them, list file Information, permission management.