Lecture 6a - Overview of Lecture 6a - Overview of operating systems operating systems

CSCI102 - Introduction to CSCI102 - Introduction to Information Technology BInformation Technology B

ITCS905 - Fundamentals of ITCS905 - Fundamentals of Information TechnologyInformation Technology

Operating SystemsOperating Systems

Purpose, varieties, pros and consPurpose, varieties, pros and cons

What is an Operating System What is an Operating System (OS) ?(OS) ?

A set of computer programs that provides A set of computer programs that provides an interface between an interface between hardware hardware application programsapplication programs

What is an Operating System What is an Operating System (OS) ?(OS) ?

When you buy a game, it will run on a When you buy a game, it will run on a wide variety of similar computers as long wide variety of similar computers as long as those computers use the same as those computers use the same operating systemoperating system

As long as the hardware is compatible with As long as the hardware is compatible with the OS and you have sufficient processing the OS and you have sufficient processing power and memory, your software should power and memory, your software should runrun

What does the OS doWhat does the OS do

The OS controls the various bits of The OS controls the various bits of hardware hardware MonitorMonitor Disc driveDisc drive MouseMouse Sound card etcSound card etc

What does the OS doWhat does the OS do

When you install an OS, you often need to When you install an OS, you often need to install “drivers” for some devicesinstall “drivers” for some devices Drivers let the OS correctly control those Drivers let the OS correctly control those

devicesdevices Applications usually communicate with the OS Applications usually communicate with the OS

rather than directly with the hardwarerather than directly with the hardware If the drivers and the OS are properly set up, If the drivers and the OS are properly set up,

the OS will ensure that application commands the OS will ensure that application commands are correctly carried outare correctly carried out

Different OS for Different Different OS for Different MachinesMachines

In different “brands” of computers, the In different “brands” of computers, the hardware is so different that each brand hardware is so different that each brand needs its own OS needs its own OS MacintoshMacintosh PCs PCs PalmPalm

Different OS for Different Different OS for Different MachinesMachines

Some brands are highly proprietorial Some brands are highly proprietorial They don’t allow non-brand components in They don’t allow non-brand components in

their systemstheir systems They usually have their own OSThey usually have their own OS

Other brands allow “clones” and multiple Other brands allow “clones” and multiple hardware configurationshardware configurations These require more complex OS and the use These require more complex OS and the use

of drivers of drivers

Multi-OS applicationsMulti-OS applications

If a software vendor wants to sell the same If a software vendor wants to sell the same software to different OS users, the vendor software to different OS users, the vendor must produce separate versions for each must produce separate versions for each OSOS Separate Mac, Windows 95, 98, NT versionsSeparate Mac, Windows 95, 98, NT versions

Managing these different versions is a big Managing these different versions is a big job for software companies and job for software companies and sometimes poses problems for purchaserssometimes poses problems for purchasers

Users’ preferencesUsers’ preferences

Users are often very loyal to the OS which Users are often very loyal to the OS which they first learn or which they currently usethey first learn or which they currently use

This has led to a lot of hostility between This has led to a lot of hostility between different OS users different OS users

Despite this, most current OS are very Despite this, most current OS are very good and have a lot to recommend themgood and have a lot to recommend them

The Computer MixThe Computer Mix

Businesses today run a mix of computer Businesses today run a mix of computer types and computer operating systemstypes and computer operating systems Pentiums running Windows 95/98 on office Pentiums running Windows 95/98 on office

desktopsdesktops Macs for graphic arts workMacs for graphic arts work Linux for Web Servers etcLinux for Web Servers etc

The Computer MixThe Computer Mix

The right mix of computers offers The right mix of computers offers “interoperability” “interoperability” Better than trying to use one type of computer Better than trying to use one type of computer

and operating system to fit all tasksand operating system to fit all tasks

Common PlatformsCommon Platforms

Common PlatformsCommon Platforms

Legacy SystemsLegacy Systems Mainframe or mini computer OS e.g. VAXMainframe or mini computer OS e.g. VAX

Microsoft Operating SystemsMicrosoft Operating Systems

UNIX SystemsUNIX Systems

Proprietary UNIX Systems (AT&T)Proprietary UNIX Systems (AT&T)

Legacy SystemsLegacy Systems

Older systems commonly providing Older systems commonly providing specific capabilities like an airline specific capabilities like an airline reservation system:reservation system: IBM mainframes running proprietary IBM OSIBM mainframes running proprietary IBM OS Unisys and other mainframes with their own Unisys and other mainframes with their own

proprietary operating systemsproprietary operating systems Digital VAX systems running VMS Digital VAX systems running VMS

Legacy SystemsLegacy Systems

Problems:Problems: Not designed to interact with other computers Not designed to interact with other computers

and operating systems and operating systems Hard (impossible) to add new capabilities to Hard (impossible) to add new capabilities to

the company computer mix the company computer mix

Microsoft OSMicrosoft OS

MS-DOS MS-DOS Windows 95, 98, 2000, NT, ME, XP Windows 95, 98, 2000, NT, ME, XP Plus: Plus: Availability of applications Availability of applications Technological InertiaTechnological Inertia

Minus:Minus: Lack of decent connectivity and interoperability Lack of decent connectivity and interoperability ’’95, 98 and NT connect fairly well to similar systems 95, 98 and NT connect fairly well to similar systems

but lack interoperability with other operating systembut lack interoperability with other operating system Encourages an “all-Microsoft'' shopEncourages an “all-Microsoft'' shop Limitations ( poor Internet connectivity and low Limitations ( poor Internet connectivity and low

security) costly to overcomesecurity) costly to overcome

UNIXUNIX

Started at AT&T, who licensed the source Started at AT&T, who licensed the source code and trade-name to various vendorscode and trade-name to various vendors

Today, the brand UNIX belongs to X/Open Today, the brand UNIX belongs to X/Open and the original source code is owned by and the original source code is owned by The Santa Cruz Operation (SCO)The Santa Cruz Operation (SCO)

Any vendor that meets testing Any vendor that meets testing requirements and pays a fee can use the requirements and pays a fee can use the UNIX nameUNIX name

POSIX POSIX

IEEE* standard for UNIX IEEE* standard for UNIX POSIX- compliant means supporting a standard POSIX- compliant means supporting a standard set of interfacesset of interfacesRelatively easy to port Applications from a Relatively easy to port Applications from a POSIX system to another POSIX systemPOSIX system to another POSIX systemSource code for the “application” must be Source code for the “application” must be availableavailable

* Institute of electrical and electronic engineers* Institute of electrical and electronic engineers

Proprietary UNIX SystemsProprietary UNIX Systems

Specific vendors develop UNIX versions that Specific vendors develop UNIX versions that only run on their hardware.: only run on their hardware.: HP/UX for Hewlett-Packard computer systemsHP/UX for Hewlett-Packard computer systems Solaris for Sun and SPARC-compatible computers Solaris for Sun and SPARC-compatible computers IRIX for Silicon Graphics computer systems IRIX for Silicon Graphics computer systems Digital UNIX for Digital Alpha computer systemsDigital UNIX for Digital Alpha computer systems AIX for IBM computer systems AIX for IBM computer systems

Also SCO UNIX Also SCO UNIX Runs on any Intel x86 and compatible chip. Runs on any Intel x86 and compatible chip.

UNIX AdvantagesUNIX Advantages

Excellent connectivityExcellent connectivity - the operating system of the Internet - the operating system of the Internet

StabilityStability Over 25 years in the marketplace, but not all Over 25 years in the marketplace, but not all

proprietary modifications included in the UNIX proprietary modifications included in the UNIX base. base.

UNIX AdvantagesUNIX Advantages

Scalability – Scalability – UNIX technology has run on the original 8086-UNIX technology has run on the original 8086-

based PC to multi-million dollar Cray based PC to multi-million dollar Cray supercomputers supercomputers

But may mean different vendors to change But may mean different vendors to change sizes sizes

Could mean purchasing new versions of Could mean purchasing new versions of applications software for the new applications software for the new vendor/architecture vendor/architecture

UNIX AdvantagesUNIX Advantages

Multi-user, multi-tasking from the startMulti-user, multi-tasking from the start

File, print and remote access servers can File, print and remote access servers can be implemented using any UNIX-based be implemented using any UNIX-based systemsystem

Open UNIX-like Open UNIX-like SolutionsSolutions

UNIX capabilities not tied to a UNIX capabilities not tied to a specific hardware vendor or specific hardware vendor or

machine architecturemachine architecture

LinuxLinux

Started out as a project by Started out as a project by LinusLinus TorvaldsTorvalds in 1991. in 1991. ““Open Source” - thousands of people - from Open Source” - thousands of people - from

students to computer professionals - got students to computer professionals - got involved in the development. involved in the development.

Linux ConnectivityLinux Connectivity

All of UNIX connectivity + more!All of UNIX connectivity + more! UNIX and POSIX capabilities as a basisUNIX and POSIX capabilities as a basis

TCP/IP connectivity TCP/IP connectivity Drivers for many serial, ISDN and Frame Relay Drivers for many serial, ISDN and Frame Relay controllers controllers Appletalk for Mac/Linux connectivity Appletalk for Mac/Linux connectivity SAMBA for Microsoft Windows/Linux SAMBA for Microsoft Windows/Linux connectivity connectivity IPX protocol support for Novell Netware/Linux IPX protocol support for Novell Netware/Linux connectivity connectivity

Other Linux AdvantagesOther Linux Advantages

Linux can grow with youLinux can grow with you E.g if you are running an Intel-based web E.g if you are running an Intel-based web

server you can upgrade to a Sun SPARC or server you can upgrade to a Sun SPARC or Digital Alpha for higher performance systemDigital Alpha for higher performance system

Linux can grow with the futureLinux can grow with the future New hardware is being introduced every yearNew hardware is being introduced every year Linux ports to new computer architecture from Linux ports to new computer architecture from

multiple vendors ASAPmultiple vendors ASAP

Other PlatformsOther Platforms

MacOS on the Apple Macintosh MacOS on the Apple Macintosh

Plus: Plus: Developed as a workstation Developed as a workstation Possibly the best workstation for graphicsPossibly the best workstation for graphics

Minus:Minus: not designed to inter-operate well with non-Mac not designed to inter-operate well with non-Mac

systems systems

  Novell Netware Novell Netware

Plus:Plus: Designed to make up for the poor connectivity Designed to make up for the poor connectivity

of early Microsoft productsof early Microsoft products Offering file server capabilities for DOS and Offering file server capabilities for DOS and

Windows-based systems but little more. Windows-based systems but little more.

Minus:Minus: interoperability of Windows95/98 and server interoperability of Windows95/98 and server

capabilities of Linux make Netware a legacy capabilities of Linux make Netware a legacy systemsystem

Selecting the Right OSSelecting the Right OS

Selecting the Right OSSelecting the Right OS

Does it address your current needs?Does it address your current needs? e.g your business requires secure, on-line WWW e.g your business requires secure, on-line WWW

transactions transactions

What sort of interoperability does it have? What sort of interoperability does it have? e.g. unlikely your accounting system runs on the e.g. unlikely your accounting system runs on the

same type of system as your web server. same type of system as your web server.

What different hardware platforms are What different hardware platforms are supported?supported? Will you have a reasonable upgrade path Will you have a reasonable upgrade path e.g.can you add more of networked computerse.g.can you add more of networked computers

Selecting the Right OSSelecting the Right OS

How Maintainable is it?How Maintainable is it? Tradeoffs Tradeoffs

Hardware support is simplified for software that runs on Hardware support is simplified for software that runs on “commodity hardware”' such as generic PC platforms“commodity hardware”' such as generic PC platforms

Some vendors offer hardware and software support Some vendors offer hardware and software support

Some operating systems come with source code or source Some operating systems come with source code or source code may be purchasedcode may be purchased

This makes support of special hardware and future expansion This makes support of special hardware and future expansion easier -- either with an internal support staff or outside easier -- either with an internal support staff or outside contractorscontractors

Single-platform solutions can easily lead to a dead endSingle-platform solutions can easily lead to a dead end

Selecting the Right OSSelecting the Right OS

Is it non-proprietary?Is it non-proprietary? Non-proprietary operating systems can make Non-proprietary operating systems can make

it easier to upgrade hardware as new it easier to upgrade hardware as new technology becomes available. technology becomes available.

Is it POSIX compatible?Is it POSIX compatible? Most prominent operating system Most prominent operating system POSIX standard compliance offers the best POSIX standard compliance offers the best

chance of long-term growth and support. chance of long-term growth and support.

OS Comparision TableOS Comparision Table

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