Overview of operating systems


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  • BSDI, NetBSD and FreeBSD systems are based BSD UNIX.
  • Overview of operating systems

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