1. The Functions of Operating Systems Network Operating Systems (NOS)

2. Learning Objectives Describe the main components of a network operating system.

3. Facilities Provided by a NOS Directory Services Accounting Software sharing Hardware sharing (including print spooling) SecurityCommunications The user interface

4. Directory Services Allow users to manage access to their own files. i.e. Normal file manipulation of a stand alone computer. i.e. Normal file manipulation of a stand alone computer. E.g. search, delete… E.g. search, delete… Prevent access to a user’s files by other unauthorised users. Maintain a directory of software / services available to specified users. Allow a set amount of storage to be allocated to users of the network. Allow storage space to be partitioned into many logical areas which can be given different access rights. E.g. E.g. Personal user storage only. Shared User Storage (by all or a selected list). Read / Write access to some users and read only to others.

5. Accounting Keep details of who has used the network, when and for how long, for what purpose and which files each user has accessed. Users could be charged for printing, amount of time spent on the network and files storage. Users could be charged for printing, amount of time spent on the network and files storage. Restrict a users' storage, the amount of paper used for printing and so on. The network manager can print out details of usage so that charges may be made.

6. Software Sharing Some applications are not installed on clients either due to lack of space or rare use. NOS must share the use of these applications. NOS must share the use of these applications. So when a user requests an application, the NOS must send a copy of that application to the user's station. So when a user requests an application, the NOS must send a copy of that application to the user's station.

7. Sharing Hardware E.g. Printers. When a user sends a file for printing, the file is split into packets. When a user sends a file for printing, the file is split into packets. As many users may wish to use a printer, the packets from different users will arrive at the print server and will have to be sorted so that the data from different users are kept separate. As many users may wish to use a printer, the packets from different users will arrive at the print server and will have to be sorted so that the data from different users are kept separate. The NOS receives these packets and stores the data in different files for different users. The NOS receives these packets and stores the data in different files for different users. When a particular file is complete, it can be added to the print queue (spooling – described earlier). When a particular file is complete, it can be added to the print queue (spooling – described earlier).

8. Security Maintain security of files by restricting access by giving different users or user types different access rights. Enforce the use of passwords and IDs to establish identities. Maintain file of users, their log ins and their rights. Allow many users to use files at the same time by allowing only one user at a time to have write access to a file and any other users only read access. Avoids corruption and inconsistency. Avoids corruption and inconsistency. Protect system files by making them read only, hiding them from users and not allowing ordinary users to change these attributes.

9. Communications The NOS will have to handle communications between stations and servers. So NOS is in each station and the other is in the server/s. These two parts must be able to communicate with one another so that messages and data can be sent around the network. There will consequently be a need for rules to govern this communication.

10. User Interface NOS must provide one between the hardware, software and user. NOS has to offer different users different interfaces. When a user logs onto a network, the NOS looks up the needs of the user and displays the appropriate icons and menus for that user, no matter which station the user uses. The NOS must also allow users to define their own interfaces within the restrictions laid down by the network manager.

11. Transparency The whole system is said to be transparent to the user if when they use it, they feel as if it were acting solely for their own use. i.e. Users are unaware of the hardware and software actions or communications. i.e. Users are unaware of the hardware and software actions or communications. A good user interface has a high level of transparency and this should be true of all operating systems.

12. Plenary Name and describe the main components of a network operating system.