1. Network Operating Systems (NOS)
Lecture 1:
Network Operating Systems (NOS)
By: Adal ALashban

2. What is an Operating System (OS)?
- A program that acts as an intermediary between a user of a computer and the computer hardware.
- Is a software that manages computer hardware and software resources and provides common services for computer programs.
- Operating systems form an essential component of the system software in a computer system.
- Application programs usually require an operating system to function.

3. Goals of Operating System (OS)
Operating system goals: 
Execute user programs and make solving user problems easier.
Make the computer system convenient to use.
Use the computer hardware in an efficient manner.

5. 2 kinds of a software: Application Software:
- Word processors, database manager, compiler, web browser.
System Software:
- Operating system itself.
- Bridges between the hardware and users.

6. Functions of Operating Systems (OS)
- Resource management.
- Memory management.
- Device management:
– Printer
– Hard drive
– display
- Process management.
- Processor management (CPU time).

8. Why OS was Born?
Batch processing
– Resident Monitor.

9. Time Sharing Using Operating Systems

10. In Operating Systems
- Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources.
- For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware.
- Operating systems can be found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

11. Examples of Operating Systems
Examples of popular modern operating systems include:
Android, BSD, iOS, Windows Phone,
Linux, OS X, QNX,
Microsoft Windows, and IBM z/OS.
All these examples, except Windows, Windows Phone and z/OS, share roots in UNIX.

13. Networks Operating Systems
- Network operating system (NOS): software that implements an operating system of some kind that is oriented to computer networking.
- The network operating system is designed to allow shared file and printer access among multiple computers in a network.

14. NOS Characteristics
- Network operating systems (NOSs) distribute their functions over a number of networked computers.
- It adds functions that allow users to access shared resources concurrently.
- Client systems contain specialized software that allows them to request shared resources that are controlled by server systems responding to a client request.

15. Differences Between PC and a NOS
- The NOS enhances the reach of the client PC by making remote services available as extensions of the local operating system.
- Although a number of users may have accounts on a PC, only a single account is active on the system at any given time.
- NOS supports multiple user accounts at the same time and enables concurrent access to shared resources by multiple clients (multitasking and multiuser environment).

17. Multiuser, Multitasking, and Multiprocessor Systems
- A NOS server is a multitasking system. the OS is capable of executing multiple tasks at the same time.
- Some systems are equipped with more than one processor, called multiprocessing systems.
- Multiprocessing systems are capable of executing multiple tasks in parallel by assigning each task to a different processor.
- The total amount of work that the server can perform in a given time is greatly enhanced in multiprocessor systems.

19. NOS Server Hardware - NOS servers are large systems with additional
memory to support multiple tasks that are all active,
or resident, in memory at the same time.
- Additional disk space is also required on servers to hold shared files and to function as an extension to the internal memory on the system.
- Because a NOS depends on the continuous operation of its servers, the extra hardware components justify the additional expense.

20. Choosing a NOS
The main features to consider when selecting a NOS include:
Performance.
Management and monitoring tools.
Security.
Scalability.
Robustness/fault tolerance.

21. Networks Operating Systems: Where to use?
NOS can be used in:
Routers, switches and hardware firewall.
PCs in Peer-to-peer networks.
Client-server Architecture.

22. Scale(size) Based Network Classification:
The basic types of networks are:
PAN
LAN
MAN
WAN
Internet

23. Personal Area Network (PAN)
- Computer network organized around an individual person.
- PAN involves a computer, a cell phone ..etc
- Using Bluetooth and USB often used to link this kind of networks.
- Communication Technology:
Wired
Wireless (WPAN): (Bluetooth, infrared)

24. Local Area Network (LAN)
- A local area network (LAN) is a privately owned network that operates within and nearby a single building like a home, office or factory.
- The connection must be high speed and inexpensive.
- Size: few kilometers.

25. Local Area Network (LAN)
Advantages:
- Easy to share.
- Cost of LAN setup is low.
Disadvantages:
- Power.
- Security.
- Speed.
- Covers limited area.

26. Metropolitan Area Network (MAN)
- A metropolitan area network (MAN) is a high-speed network that connects local area networks in a metropolitan area.
- It covers a city.
- Examples:
The cable television networks available in many cities.

27. Metropolitan Area Network (MAN)
Advantages:
- Efficiency and shared access.
- All the computers residing in the same area have an equal chance to access the network.
Disadvantages:
- Costly.
- Security problems.
- slow.

28. Wide Area Network (WAN)
- A wide area network (WAN) is a network that covers a large geographic area.
- Such as a city, country, or the world) using a communications channel that combines many types of media.
- Examples:
The telephone lines, cables, and radio waves.

29. Wide Area Network (WAN)
Advantages:
- Increased efficiency.
- Ease of communication.
Disadvantages:
- Security problems.
- Training costs.
- Maintenance problems.

30. Thank You