Multi tasking is when the operating system seems to be performing two or more tasks at the same time, i.e. MS Word and MS Access, however these tasks are not actually running simultaneously as they are actually resident in memory processor is actually switching between tasks at a very high speed, therefore each user sees their own task as having priority. One disadvantage can be that the more programs that are run by the user, the more memory that is required. Multi Tasking can be split into two categories, co-operative and pre-emptive.
Co-operative is when the process currently controlling the CPU must offer a balanced share of the CPU to all other processes, hence Co-operative, as all processes must co-operate for it to work properly. Subsequently an MUOS will allow two or more users a share of the system resources at the same time. The use of the resources must be spread evenly between the requirements of the users so that a problem with one user does not become a problem between all users. Examples of co-operative multi tasking would be Windows 3x and Macintosh.
Pre-emptive is when the applications are forced to share the CPU whether they want to or not and examples of this are Windows 95, NT and UNIX.
How print sharing operates?
NOS – A print server allows multiple users access to a single printer. A print server will also give you information on the use of the printer. All print jobs are sent to a Network Printer, controlled by the server, where they will wait in turn to be printed. For example, you can:
See how many people are using the printer;
Set limits to the usage;
Give higher priority to some workstations, allowing them to print before others;
See who is currently printing or;
See when your print job is coming up.
MUOS – The Multi-User Operating System Linux uses a printing system called LPD, which constantly runs as a background process and acts as a spooler for files when they are required to be printed. Spooling (Simultaneous Peripheral Operations On-Line) is where all input/output of non-shareable devices is redirected to an intermediate shareable device. This is done, for example to stop other processes queuing for long periods of time to access a certain device. The most common form of spooling would be print spooling, where documents are printed at the printer’s own rate after being loaded into an intermediate shareable area (buffer).) is where all input/output of non-shareable devices is redirected to an intermediate shareable device. This is done, for example to stop other processes queuing for long periods of time to access a certain device. The most common form of spooling would be print spooling, where documents are printed at the printer’s own rate after being loaded into an intermediate shareable area (buffer).
System Failure and Robustness
On a MUOS, data must be backed up on a regular basis, as if the server goes down then all unsaved work or data on the network is lost. It is therefore necessary to make a hard copy of all-important data. It is also important to have a recovery disc made upon installation. However, on a Network Operating System there is a system failure then only the unsaved data on the actual client is lost and not across the entire Network. The clients will still be almost fully operational without the server itself.
A Multi-User Operating System tends to be a lot more robust than a Network Operating System. It is widely recognised that windows in particular is very unpredictable at times and is prone to fatal errors. This is not the case with the likes of Unix or Linux.
Application, file sharing and file locking
File sharing is a very important part of a Network Operating System. Users will continuously need to access and share the same files across a network and giving them usernames and passwords can do this. However if two or more users were to try and access the same file (for example, a Word document) at the same time and both users on the Network had read and write access, then only one user would be granted access at a time and the other would be denied. This concept is known as File Locking. This could be looked upon as a basic traffic system, if you like, where as soon as one user has access to a file then the red light is switched on. Then, when the first user has finished with the particular file, the green light shows and the second user is free to access the data. In a Multi User Operating System, you would find a different method known as NFS (Network File System). This is a where the server or Network Administrator can control which users can have which type of access to different applications or files at specific times.
Architecture & Clients
A Network Operating System uses a Graphical User Interface, as it is part of the Microsoft Windows family, which are all GUI’s. This makes the Operating System much easier to use in many ways such as being more user friendly and easier to learn.
However a Multi-User Operating System like Unix for example would use a Command Line Interface. This has its good and bad points being that the user has greater level of control over commands; the System is more stable and does not use excessive system resources. On the other hand, the users would have to familiarise themselves with a lot of commands which can be time consuming. Both have the Kernel as the heart of the Operating System. This is the part of the operating system that loads first, and it remains in main memory and typically, is responsible for memory management, I/O system management, file system management, process and task management and scheduling, and disk management. The Kernel is essentially the “nucleus” of the operating system that provides basic services for all other components of the operating system. For each process, the Kernel holds a process identifier, the user identity and the size and location of the process. A Network Operating System and a Multi-User Operating System will normally operate using “Thick “and “Thin ” clients respectively:
No hard disk on client
Connected to a server
Applications run on server
Data stored on server
Mouse, Video, Keyboard etc. through which you can access server
Can support sound, CD-ROM etc.
Client has own hard disk
Client has storage space
Client can have own applications stored
Basically the opposite of “Thin clients”
A Network Operating System can support many hundreds of clients across a Local Area Network as can a Multi User Operating System.
Protocols and Internetworking
In order for a Network Operating System to send or receive data, the data must be broken down into packets by a method called a protocol. Windows NT uses the IPX/SPX, NetBEUI, and TCP/IP protocols for network communication. Netware uses IPX/SPX. UNIX, Linux, and the Internet all use TCP/IP. While different protocols usually cannot talk directly with each other, most Network Operating Software can understand more than one protocol. This also adds the possibility of Internetworking for most Network operating Systems as they can communicate freely over different Networks unlike MUOS.
Both types of operating system (NOS and MUOS) have built-in TCP/IP networking, for communications across all forms of networks, and between all forms of computers. Other Protocols and the respective layers of the OSI models at which they operate are shown here: –
Application – Telnet, HTML
Presentation – SMB, NCP
Session – NETBIOS (NETBEUI)
Transport – TCP
Network – IP. TCP/IP, IPX/SPX
Data Link – Ethernet
Physical – Radio
Multi User Operating Systems are far more scalable because they can run on literally every hardware platform, from the slowest hardware to the world’s fastest. Additionally, most UNIX operating systems support more than one processor, so a machine configured with 4 processors can support many more users than a machine with one processor of the same type.
Security measures are very important on any Operating System. On a Network operating System such as Win 2000 server it would be fairly easy to install some sort of security software (Firewall) such as one of the Norton Internet Security packages. Anti-virus software is also readily available and very widely used. With a Multi-User Operating System such as Unix, there are a number of security tools available to download as Freeware that perform a vast array of different tasks relating to security.
Hardware requirements: the Typical Hardware requirements for installing two different Operating Systems (Linux and windows 2000 server) are shown here below (minimum and recommended):
200 MHZ Processor required
650MB Hard Drive
NOS (Windows 2000 Server)
Pentium compatible 133MHZ or faster
2GB Hard Drive
Pentium II 200MHZ
256 MB RAM
9GB Hard Drive
Financially, Multi-User a Operating System would be much more viable than a Network Operating System due to the fact that the MUOS can use dumb Terminals, which basically means that the majority of the hardware and more importantly software is on the actual server i.e. the clients (workstations) have only the essential components needed to operate. These would include Keyboard, Mouse, monitor etc. however in the event of having a very large Network this could in effect end up equally as costly as a Network Operating System.
Role of Network Administrator
The role of a network administrator in large companies and consulting firms may be only managing network servers, adding users, and adding printers. However, most network administrators also do some desktop support as well as controlling network addresses, protocols used, and the network interfaces because these are all obviously network components. The network administrator will also control routing, name resolution, and assignment of TCP and UDP socket numbers because, again, these are all pretty clearly network specific components. In small companies, day-to-day network administration is often not a full time job and is assigned as a part-time task to someone in the office. To troubleshoot a network you must understand things, such as: how individual PCs work, general networking concepts, and product specific features.
A network administrator is a manager: not of people but of computing resources. A network administrator is creating and managing user accounts, installing and maintaining print services, ensuring that the network is running smoothly and that the computers are running efficiently, maintaining the integrity of the network, handling user complaints, and so forth. Users would be allowed access to system resources by means of a user account, which would be set up and then users would be allocated a username and password(s). This would allow the Network Administrator to set different security levels for different clients and users. For example, within a company or Business, you would have different levels of access for different levels of staff members with management having access to more resources and data than perhaps an office junior etc.
A network administrator should be able to manage resources by doing the following:
Creating, managing and utilizing Windows 2000 shared folders
Using the Distributed File System to provide easy access to network resources
Using the Windows 2000 events logs to monitor system and application activities
Using the Task Manager to observe and monitor resources
Using the System Monitor in the Performance tool to optimize performance
Using security policies to protect data and system integrity
Using auditing to track security events
The Network Administrator is also responsible for budgeting decisions regarding the Network itself. This would involve very closely monitoring each and every client, making decisions on whether new hardware or software is required and when. Any Firewalls or Antivirus software would also have to be updated continuously.
Dick, David (2002) The P.C. Support Handbook. Kirkintilloch: Dumbreck Publishing