Transcript 3. Data Communications

3. Data
Communications
3.3 Network Operating
Systems
Operating Systems (OS)



The master control program that runs the
computer.
It is the first program loaded when the
computer is turned on, and its main part,
called the "kernel," resides in memory at all
times.
It may be developed by the vendor of the
computer it's running in or by a third party.
Operating Systems (OS)
It is an important component of the
computer system, because it sets the
standards for the application programs
that run in it.
 All programs must "talk to" the
operating system.

Functions of OS
(explained
by techweb.com)
User Interface
 Job Management
 Task Management
 Data Management
 Device Management
 Security

(From www.techweb.com)
Functions of OS

Program execution
– Load the program into the main memory and run
the program

I/O operations
– Control the selection and use of input and output
devices

File maintenance
– Storage, create, delete and rename files

Error detection
– Alert the user when errors occur, e.g. insufficient
memory, power failure or out of paper
(From Computer Studies for the New Generation, W.H.Kwan, Chung Tai Educational Press)
Functions of OS



Security control
– Check the user identity and password. If an
unauthorised user is suspected, the access right will
be denied
Resources allocation
– Allocate the CPU time, main memory and I/O devices
to the user. Resources allocation is very important
when the computer is shared by different users
Job scheduling
– Set priorities for the jobs. The operating system has
to arrange a job processing sequence for the CPU
and to respond to computer users within an
appropriate time
(From Computer Studies for the New Generation, W.H.Kwan, Chung Tai Educational Press)
Network OS (NOS)



an operating system that manages network
resources
manages multiple requests (inputs)
concurrently and provides the security
necessary in a multiuser environment
It may be a completely self-contained
operating system, such as NetWare, UNIX
and Windows NT, or it may require an
existing operating system in order to
function (LAN Server requires OS/2;
LANtastic requires DOS, etc.)
(From www.techweb.com)
More about NOS
In a peer-to-peer network, the network
operating system allows each station
to be both client and server
 In a non-peer-to-peer network,
dedicated servers are used, and files
on a client machine cannot be
retrieved by other users

More about NOS


In networks of PCs, NetWare is the most
widely used network operating system.
Windows NT, Windows for Workgroups,
Windows 95/98, VINES, LAN Server, LAN
Manager and LANtastic are also examples
UNIX, combined with TCP/IP and NFS,
VMS combined with DECnet, the Mac OS
combined with AppleTalk, and SNA,
combined with VTAM and NCP, also provide
network operating system services
Differences between
OS and NOS



The main difference between an operating
system and a network operating system is
its multiuser capability
Operating systems, such as Macintosh
System 7, DOS and Windows, are single
user, designed for one person at a desktop
computer
Windows NT and UNIX on the other hand
are network operating systems, because
they are designed to manage multiple user
requests at the same time