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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) ?.

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lecture 6a overview of operating systems

Lecture 6a - Overview of operating systems

CSCI102 - Introduction to Information Technology B

ITCS905 - Fundamentals of Information Technology

operating systems

Operating Systems

Purpose, varieties, pros and cons

what is an operating system os
What is an Operating System (OS) ?
  • A set of computer programs that provides an interface between
    • hardware
    • application programs
what is an operating system os1
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
What does the OS do
  • The OS controls the various bits of hardware
    • Monitor
    • Disc drive
    • Mouse
    • Sound card etc
what does the os do1
What does the OS do
  • When you install an OS, you often need to install “drivers” for some devices
    • 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
Different OS for Different Machines
  • In different “brands” of computers, the hardware is so different that each brand needs its own OS
    • Macintosh
    • PCs
    • Palm
different os for different machines1
Different OS for Different Machines
  • Some brands are highly proprietorial
    • They don’t allow non-brand components in their systems
    • They usually have their own OS
  • Other brands allow “clones” and multiple hardware configurations
    • These require more complex OS and the use of drivers
multi os applications
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
    • 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’ 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
The Computer Mix
  • Businesses today run a mix of computer types and computer operating systems
    • Pentiums running Windows 95/98 on office desktops
    • Macs for graphic arts work
    • Linux for Web Servers etc
the computer mix1
The Computer Mix
  • The right mix of computers offers “interoperability”
    • Better than trying to use one type of computer and operating system to fit all tasks
common platforms1
Common Platforms
  • Legacy Systems
    • Mainframe or mini computer OS e.g. VAX
  • Microsoft Operating Systems
  • UNIX Systems
  • Proprietary UNIX Systems (AT&T)
legacy systems
Legacy Systems
  • Older systems commonly providing specific capabilities like an airline reservation system:
    • IBM mainframes running proprietary IBM OS
    • Unisys and other mainframes with their own proprietary operating systems
    • Digital VAX systems running VMS
legacy systems1
Legacy Systems
  • Problems:
    • Not designed to interact with other computers and operating systems
    • Hard (impossible) to add new capabilities to the company computer mix
microsoft os
Microsoft OS
  • MS-DOS  Windows 95, 98, 2000, NT, ME, XP
  • Plus:
    • Availability of applications
    • Technological Inertia
  • Minus:
    • 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
  • 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
  • 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
Proprietary UNIX Systems
  • Specific vendors develop UNIX versions that only run on their hardware.:
    • 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
    • Runs on any Intel x86 and compatible chip.
unix advantages
UNIX Advantages
  • Excellent connectivity
    • - the operating system of the Internet
  • Stability
    • Over 25 years in the marketplace, but not all proprietary modifications included in the UNIX base.
unix advantages1
UNIX Advantages
  • Scalability –
    • 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 advantages2
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

Open UNIX-like Solutions

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

  • Started out as a project by Linus Torvalds in 1991.
    • “Open Source” - thousands of people - from students to computer professionals - got involved in the development.
linux connectivity
Linux Connectivity
  • All of UNIX connectivity + more!
    • 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
Other Linux Advantages
  • Linux can grow with you
    • 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
    • New hardware is being introduced every year
    • Linux ports to new computer architecture from multiple vendors ASAP
macos on the apple macintosh
MacOS on the Apple Macintosh
  • Plus:
    • Developed as a workstation
    • Possibly the best workstation for graphics
  • Minus:
    • not designed to inter-operate well with non-Mac systems
novell netware
 Novell Netware
  • Plus:
    • 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:
    • interoperability of Windows95/98 and server capabilities of Linux make Netware a legacy system
selecting the right os1
Selecting the Right OS
  • Does it address your current needs?
    • e.g your business requires secure, on-line WWW transactions
  • What sort of interoperability does it have?
    • e.g. unlikely your accounting system runs on the same type of system as your web server.
  • What different hardware platforms are supported?
    • Will you have a reasonable upgrade path
    • e.g.can you add more of networked computers
selecting the right os2
Selecting the Right OS
  • How Maintainable is it?
    • 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
        • 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 os3
Selecting the Right OS
  • Is it non-proprietary?
    • Non-proprietary operating systems can make it easier to upgrade hardware as new technology becomes available.
  • Is it POSIX compatible?
    • Most prominent operating system
    • POSIX standard compliance offers the best chance of long-term growth and support.