Lecture 6a - Overview of operating systems

1. Lecture 6a - Overview of operating systems CSCI102 - Introduction to Information Technology B ITCS905 - Fundamentals of Information Technology

2. Operating Systems Purpose, varieties, pros and cons

3. What is an Operating System (OS) ? • A set of computer programs that provides an interface between • hardware • application programs

4. 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

5. What does the OS do • The OS controls the various bits of hardware • Monitor • Disc drive • Mouse • Sound card etc

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. Common Platforms

14. Common Platforms • Legacy Systems • Mainframe or mini computer OS e.g. VAX • Microsoft Operating Systems • UNIX Systems • Proprietary UNIX Systems (AT&T)

15. 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

16. Legacy Systems • Problems: • Not designed to interact with other computers and operating systems • Hard (impossible) to add new capabilities to the company computer mix

17. 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

18. 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

19. 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

20. 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.

21. 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.

22. 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

23. UNIX Advantages • Multi-user, multi-tasking from the start • File, print and remote access servers can be implemented using any UNIX-based system

24. Open UNIX-like Solutions UNIX capabilities not tied to a specific hardware vendor or machine architecture

25. Linux • 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.

26. 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

27. 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

28. Other Platforms

29. 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

30.  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

31. Selecting the Right OS

32. 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

33. 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

34. 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.

35. OS Comparision Table Free Free