Transcript what are the three "core/key skills"?

COMP1321
Digital Infrastructure
Richard Henson
University of Worcester
January 2016
Week 12: Network
Operating Systems
Explain how client-server and peer-peer
systems communicate and function
 Explain the dual role of any operating
system
 Explain the various essential roles of
specialised software in a network
operating system

Functions of an
Operating System

Coordinate hardware so it all works
together cooperatively

Provide a means for human input into
the system that can control the
hardware components
Early Operating Systems

Each of the early computers was
unique
 each had to have its own purpose-built
operating system

IBM: world’s first mass produced
“mainframe”
 IBM 701 (1952)
» purchasers expected to write their the
operating system themselves!
First British Operating system

Leo 3…. first mass produced British
Computer
 94 units built 1961-1969
» full list of buyers http://www.leocomputers.org.uk/newleo3s.htm
 Features:
» loudspeaker connected to the CPU… so operators
could tell if it was “looping”
» multi-tasking operating system called “master
program”

Some continued in service until 1981
IBM Leads the world…

As well as massive computers, IBM
started to produce operating systems
first “mass produced” operating system
written by General Motors: GM-NAA I/O in
1956
soon adopted by IBM… as IBSYS

IBM hugely successful…
by 1980s, able to defeat US government in
a legal case
First Minicomputer
& Operating system

Digital Equipment Corporation (DEC), 1963
 PDP-6,7,8, etc.
» “mini” in size compared to mainframes
» huge by today's standards
 operating system: “monitor”
»
»
»
»
evolved into the TOPS10 (1970)
still going until 1988
can get it even now:
http://www.inwap.com/pdp10/96license.txt
Unix

Spin-off (1969) from project MULTICS
 First attempt at a multiuser operating system
» Consortium including Bell Labs, AT&T,

US equivalent of BT at that time
» FAILED! Too ambitious…
 Bell Labs: cut down version UNICS -> UNIX
» written in assembly language by Ken Thompson
» sharing of processes also being explored by ARPAnet
project
 Commercial Challenge:
 DEC PDP-7,8, etc. minicomputer needed a general purpose
“time sharing” operating system for multiuser use…
 os “monitor” had not yet matured into TOPS-10
Thompson, Ritchie,
“B”, NB, “C” & Unix

Thompson looking for a high-level language
to develop a time sharing os
• briefly toyed with Fortran
• worked with colleague Dennis Ritchie to create
their own higher level language – “B”, based on
BCPL
» http://cm.bell-labs.com/cm/cs/who/dmr/kbman.html
• development of B = newB (NB)
• development of NB -> C
• Unix kernel was rewritten in “C” (1973)
Development of Unix/C
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“C” compiler completed by Ritchie in 1972
Further commercial Unix versions (for
Honeywell & IBM) released in 1973
“C” further developed during 1973-7
Full definition of language as Kernighan &
Ritchie “C” (1978)
 rapidly gained universal acclaim

Unix still written in “C” to present day!
 32-bit processing from the outset
Open Sourceness of Unix
 AT&T not allowed to be a commercial
company
• could not sell Unix
• gave a copy away free to any developer who
wanted to use it!
• many universities contributed to its development
 Result (in 1979): Unix version 7
• still recognisable today!
Silicon Valley, TCP/IP and Unix
 University of California: ARPAnet (1969)
• developed TCP/IP
• 1980, gained approval through RFC
• operating system that would support TCP/IP
arrived in 1983…
» Berkeley Unix (v4.2) packaged with TCP/IP protocol
stack
» Sun Microsystems producing the hardware…
 Silicon Valley:
• IT hot spot around SF developed from 1975…
Bell Labs Unix becomes
Commercial…
 US Dept of Justice broke up AT&T in 1984
• Bell Labs then allowed to sell their Unix source
code…
 Fortunately for SCO (Santa Cruz Operations)
they had ported Bell Unix to Intel hardware
the previous year (!)
• SCO Unix for PC became a lucrative business
market
• operating system provided security on a PC where
DOS couldn’t…
Bad days for Unix…

Unix free by nature from outset
not so on an Intel PC, thanks to SCO!!!
Bell Labs jealously guarded the source
code…
universities lost interest

Unix became expensive to buy… and
was still not user-friendly or easy to use
so even more expensive to own!
Linux

From 1992 (Linus Torvalds, University of
Helsinki) made free Unix possible again!
 LINUX – based on his name…

Took…
 Stallman’s GNU open source Unix
» which Tanenbaum had developed into MINIX…
 very stable
 secure file system
 very efficient, optimised code
 earlier versions ran on an Intel 486!

Still Unix, still a server-end system
 for client-server networking, need client-end
software:
» e.g. Banyan VINES
Linux

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
Still freely available via Internet!
Huge range of software tools for managing
UNIX networks available for download
Problems (compared to Windows):
 not as easy to manage
 limited on-screen help
 limited range of good application software
 not all hardware has UNIX/LINUX driver software
Group exercise

Consider something that you’d like
computer to do for you….
What do you want to happen?
Which hardware must do what to make
that a reality?
Specialised Functions of a
Network Operating System
Support for communication protocols
and e.g. the TCP/IP stack
 All of the centralised tasks needed to
keep the network running normally
 All achieved through software:


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highly optimised
executes code as quickly as possible…
Memory Management
Based on good use of addressing
 All programs and their data stored
within fixed memory location blocks
 Need to ensure that there is no memory
“creep”

Virtual Memory Management

Extra space on hard disk

Data constantly being swapped
between main memory and virtual
memory to maximise performance
Disk Management
Ensure data accessed from and
directed to right addresses
 Partitioning and formatting new disks
and areas of disk
 Using mirroring, duplexing and RAID as
appropriate to maximise disk
performance

File Management

Choice of filing system when
formatting
FAT?
FAT32?
NTFS
Others?
IP address Management
Most networks now use IP addresses
 System needed to manage IP
addresses across the network…
 Dynamic Host Configuration Protocol
 Managed as client-server

User and Group Management
New users have to be defined
 Users have to be allocated to groups
 Group have to be defined so as to allow
appropriate access so people can do
their jobs efficiently

User Authentication

Usernames & passwords have to be
matched against a database to ensure
granting of access is justified

Resources made available depending
on status (group) of username
Store of Network Information
Computer names and
addresses
 Device names
 Group and User names
 Service names…

Transferring Data efficiently
to another Device
Some will get corrupted en
route…
 Error(s) need to be detected
 Request then follows to resend
the data
 Part of communication protocol
