What Are The Goals Of Operating System?

An operating system has two goals
-efficient use of a computer system &
-user convenience
an operating system must not only ensure efficient use of a computer system,but also provide user convenience.
Facet of user convenience
facets                                                              example
necessity                              ability to execute programs, use the file system
good service                      speedy response to computational requests
user friendly OS                easy-to-use commands,Graphical user interface
                                                    (GUI)
new programming            concurrent programming
model
features for experts          means to set up complex computational
                                              structures
web-oriented features      means to set up web-enabled servers
evolution                            ability ti add new features,use new computers