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 hardware hardware application programs 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 Monitor Monitor Disc drive Disc drive Mouse Mouse Sound card etc Sound card etc

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 Drivers let the OS correctly control those devices Applications usually communicate with the OS rather than directly with the hardware 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 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 Macintosh Macintosh PCs PCs Palm Palm

Different OS for Different Machines Some brands are highly proprietorial They don’t allow non-brand components in their systems They don’t allow non-brand components in their systems They usually have their own OS They usually have their own OS Other brands allow “clones” and multiple hardware configurations These require more complex OS and the use of drivers 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 Separate Mac, Windows 95, 98, NT versions 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 Pentiums running Windows 95/98 on office desktops Pentiums running Windows 95/98 on office desktops Macs for graphic arts work Macs for graphic arts work Linux for Web Servers etc Linux for Web Servers etc

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 Better than trying to use one type of computer and operating system to fit all tasks

Common Platforms

Legacy Systems Mainframe or mini computer OS e.g. VAX 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: IBM mainframes running proprietary IBM OS IBM mainframes running proprietary IBM OS Unisys and other mainframes with their own proprietary operating systems Unisys and other mainframes with their own proprietary operating systems Digital VAX systems running VMS Digital VAX systems running VMS

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

Microsoft OS MS-DOS  Windows 95, 98, 2000, NT, ME, XP Plus: Availability of applications Availability of applications Technological Inertia Technological InertiaMinus: Lack of decent connectivity and interoperability Lack of decent connectivity and interoperability ’95, 98 and NT connect fairly well to similar systems but lack interoperability with other operating system ’95, 98 and NT connect fairly well to similar systems but lack interoperability with other operating system Encourages an “all-Microsoft'' shop Encourages an “all-Microsoft'' shop Limitations ( poor Internet connectivity and low security) costly to overcome 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.: HP/UX for Hewlett-Packard computer systems HP/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 systems Digital UNIX for Digital Alpha computer systems AIX for IBM computer systems AIX for IBM computer systems Also SCO UNIX Runs on any Intel x86 and compatible chip. Runs on any Intel x86 and compatible chip.

UNIX Advantages Excellent connectivity - the operating system of the Internet - the operating system of the InternetStability Over 25 years in the marketplace, but not all proprietary modifications included in the UNIX base. Over 25 years in the marketplace, but not all proprietary modifications included in the UNIX base.

UNIX Advantages Scalability – UNIX technology has run on the original 8086-based PC to multi-million dollar Cray supercomputers UNIX technology has run on the original 8086-based PC to multi-million dollar Cray supercomputers But may mean different vendors to change sizes But may mean different vendors to change sizes Could mean purchasing new versions of applications software for the new vendor/architecture 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 Linus TorvaldsLinus Torvalds “Open Source” - thousands of people - from students to computer professionals - got involved in the development. “Open Source” - thousands of people - from students to computer professionals - got involved in the development.

BSD Plus: Offers all the UNIX capabilities you would expect Offers all the UNIX capabilities you would expectMinus: Diverges from the mainstream UNIX (and POSIX) capabilities Diverges from the mainstream UNIX (and POSIX) capabilities Only run on x86 processors Only run on x86 processors Less attractive for general business solution Commonly used in dedicated systems such as routers

Linux Connectivity All of UNIX connectivity + more! UNIX and POSIX capabilities as a basis 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 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 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 New hardware is being introduced every year Linux ports to new computer architecture from multiple vendors ASAP Linux ports to new computer architecture from multiple vendors ASAP

Other Platforms

MacOS on the Apple Macintosh Plus: Developed as a workstation Developed as a workstation Possibly the best workstation for graphics Possibly the best workstation for graphicsMinus: not designed to inter-operate well with non-Mac systems 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 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. 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 interoperability of Windows95/98 and server capabilities of Linux make Netware a legacy system

Selecting the Right OS

Does it address your current needs? e.g your business requires secure, on-line WWW transactions 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. 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 Will you have a reasonable upgrade path e.g.can you add more of networked computers e.g.can you add more of networked computers

Selecting the Right OS How Maintainable is it? Tradeoffs Tradeoffs Hardware support is simplified for software that runs on “commodity hardware”' such as generic PC platforms 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 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? Non-proprietary operating systems can make it easier to upgrade hardware as new technology becomes available. Non-proprietary operating systems can make it easier to upgrade hardware as new technology becomes available. Is it POSIX compatible? Most prominent operating system Most prominent operating system POSIX standard compliance offers the best chance of long-term growth and support. POSIX standard compliance offers the best chance of long-term growth and support.

OS Comparision Table Free