Transcript The Computer Mix - University of Wollongong

Lecture 6a - Overview of
operating systems
CSCI102 - Introduction to
Information Technology B
ITCS905 - Fundamentals of
Information Technology
Operating Systems
Purpose, varieties, pros and cons
What is an Operating System
(OS) ?
A set of computer programs that provides
an interface between
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hardware
application programs
What is an Operating System
(OS) ?
When you buy a game, it will run on a
wide variety of similar computers as long
as those computers use the same
operating system
As long as the hardware is compatible with
the OS and you have sufficient processing
power and memory, your software should
run
What does the OS do
The OS controls the various bits of
hardware
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Monitor
Disc drive
Mouse
Sound card etc
What does the OS do
When you install an OS, you often need to
install “drivers” for some devices
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Drivers let the OS correctly control those
devices
Applications usually communicate with the OS
rather than directly with the hardware
If the drivers and the OS are properly set up,
the OS will ensure that application commands
are correctly carried out
Different OS for Different
Machines
In different “brands” of computers, the
hardware is so different that each brand
needs its own OS
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Macintosh
PCs
Palm
Different OS for Different
Machines
Some brands are highly proprietorial
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They don’t allow non-brand components in
their systems
They usually have their own OS
Other brands allow “clones” and multiple
hardware configurations
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These require more complex OS and the use
of drivers
Multi-OS applications
If a software vendor wants to sell the same
software to different OS users, the vendor
must produce separate versions for each
OS
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Separate Mac, Windows 95, 98, NT versions
Managing these different versions is a big
job for software companies and
sometimes poses problems for purchasers
Users’ preferences
Users are often very loyal to the OS which
they first learn or which they currently use
This has led to a lot of hostility between
different OS users
Despite this, most current OS are very
good and have a lot to recommend them
The Computer Mix
Businesses today run a mix of computer
types and computer operating systems
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Pentiums running Windows 95/98 on office
desktops
Macs for graphic arts work
Linux for Web Servers etc
The Computer Mix
The right mix of computers offers
“interoperability”
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Better than trying to use one type of computer
and operating system to fit all tasks
Common Platforms
Common Platforms
Legacy Systems
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Mainframe or mini computer OS e.g. VAX
Microsoft Operating Systems
UNIX Systems
Proprietary UNIX Systems (AT&T)
Legacy Systems
Older systems commonly providing
specific capabilities like an airline
reservation system:
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IBM mainframes running proprietary IBM OS
Unisys and other mainframes with their own
proprietary operating systems
Digital VAX systems running VMS
Legacy Systems
Problems:
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Not designed to interact with other computers
and operating systems
Hard (impossible) to add new capabilities to
the company computer mix
Microsoft OS
MS-DOS  Windows 95, 98, 2000, NT, ME, XP
Plus:
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Availability of applications
Technological Inertia
Minus:
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Lack of decent connectivity and interoperability
’95, 98 and NT connect fairly well to similar systems
but lack interoperability with other operating system
Encourages an “all-Microsoft'' shop
Limitations ( poor Internet connectivity and low
security) costly to overcome
UNIX
Started at AT&T, who licensed the source
code and trade-name to various vendors
Today, the brand UNIX belongs to X/Open
and the original source code is owned by
The Santa Cruz Operation (SCO)
Any vendor that meets testing
requirements and pays a fee can use the
UNIX name
POSIX
IEEE* standard for UNIX
POSIX- compliant means supporting a standard
set of interfaces
Relatively easy to port Applications from a
POSIX system to another POSIX system
Source code for the “application” must be
available
* Institute of electrical and electronic engineers
Proprietary UNIX Systems
Specific vendors develop UNIX versions that
only run on their hardware.:
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HP/UX for Hewlett-Packard computer systems
Solaris for Sun and SPARC-compatible computers
IRIX for Silicon Graphics computer systems
Digital UNIX for Digital Alpha computer systems
AIX for IBM computer systems
Also SCO UNIX
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Runs on any Intel x86 and compatible chip.
UNIX Advantages
Excellent connectivity
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- the operating system of the Internet
Stability
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Over 25 years in the marketplace, but not all
proprietary modifications included in the UNIX
base.
UNIX Advantages
Scalability –
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UNIX technology has run on the original
8086-based PC to multi-million dollar Cray
supercomputers
But may mean different vendors to change
sizes
Could mean purchasing new versions of
applications software for the new
vendor/architecture
UNIX Advantages
Multi-user, multi-tasking from the start
File, print and remote access servers can
be implemented using any UNIX-based
system
Open UNIX-like
Solutions
UNIX capabilities not tied to a
specific hardware vendor or
machine architecture
Linux
Started out as a project by Linus Torvalds
in 1991.
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“Open Source” - thousands of people - from
students to computer professionals - got
involved in the development.
Linux Connectivity
All of UNIX connectivity + more!
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UNIX and POSIX capabilities as a basis
TCP/IP connectivity
Drivers for many serial, ISDN and Frame Relay
controllers
Appletalk for Mac/Linux connectivity
SAMBA for Microsoft Windows/Linux
connectivity
IPX protocol support for Novell Netware/Linux
connectivity
Other Linux Advantages
Linux can grow with you
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E.g if you are running an Intel-based web
server you can upgrade to a Sun SPARC or
Digital Alpha for higher performance system
Linux can grow with the future
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New hardware is being introduced every year
Linux ports to new computer architecture from
multiple vendors ASAP
Other Platforms
MacOS on the Apple Macintosh
Plus:
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Developed as a workstation
Possibly the best workstation for graphics
Minus:
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not designed to inter-operate well with non-Mac
systems
Novell Netware
Plus:
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Designed to make up for the poor connectivity
of early Microsoft products
Offering file server capabilities for DOS and
Windows-based systems but little more.
Minus:
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interoperability of Windows95/98 and server
capabilities of Linux make Netware a legacy
system
Selecting the Right OS
Selecting the Right OS
Does it address your current needs?
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e.g your business requires secure, on-line WWW
transactions
What sort of interoperability does it have?
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e.g. unlikely your accounting system runs on the
same type of system as your web server.
What different hardware platforms are
supported?
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Will you have a reasonable upgrade path
e.g.can you add more of networked computers
Selecting the Right OS
How Maintainable is it?
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Tradeoffs
Hardware support is simplified for software that runs on
“commodity hardware”' such as generic PC platforms
Some vendors offer hardware and software support
Some operating systems come with source code or source
code may be purchased
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This makes support of special hardware and future expansion
easier -- either with an internal support staff or outside
contractors
Single-platform solutions can easily lead to a dead end
Selecting the Right OS
Is it non-proprietary?
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Non-proprietary operating systems can make
it easier to upgrade hardware as new
technology becomes available.
Is it POSIX compatible?
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Most prominent operating system
POSIX standard compliance offers the best
chance of long-term growth and support.
OS Comparision Table
Free
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