unit1.pdf - Unit-1 Introduction to Operating Systems and...

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Unit-1: Introduction to Operating Systems and System Structures Y. R. Sudhakar
The material included here is primarily from Chapter 1 & 2 and accompanying slides of Operating System Concepts by Albert Silbershatz, Peter B. Galvin & Greg Gagne , 8 th Edition
What is an Operating System ? A program that acts as an intermediary between a user of a computer and the computer hardware. OR Operating systems provide a software platform on top of which other programs, called application programs, can run. Operating system goals: Execute user programs and make solving user problems easier. Make the computer system convenient to use. Use the computer hardware in an efficient manner.
Four components of a Computer System Computer System = HW + OS + System Applications + User Applications
Operating System Definition OS serves as interface between HW and ( Apps & Users ) OS provides services for Apps & Users OS manages resources ( Government model, it doesn't produce anything. ) Debates about what is included in the OS - Just the kernel, or everything the OS vendor ships? For example, Ubuntu contains Linux kernel , KDE, compilers, system administration tools,clock application, editor, etc Solaris Operating Environment SunOS kernel , GNOME, compilers, system administration tools,clock application, editor, etc In this class, we discuss the need for and design of the various components of OS Kernel
Why study Operating System ? To learn how to extract the most efficient performance from a computer system Understand system performance Behavior of OS impacts entire machine Challenge to understand large, complex system Tune workload performance Apply knowledge across many areas Computer architecture, programming languages, data structures and algorithms, and performance modeling
Computer System Organization
What are all the parts and how they fit together?
Computer Startup bootstrap program is loaded at power-up or reboot Typically stored in ROM or EPROM, generally known as firmware Initializes all aspects of system Loads operating system kernel and starts execution
Computer-System Operation I/O devices and the CPU can execute concurrently Each device controller is in charge of a particular device type Each device controller has a local buffer CPU moves data from/to main memory to/from local buffers I/O is from the device to local buffer of controller Device controller informs CPU that it has finished its operation by causing an interrupt
Common Functions of Interrupts Interrupt transfers control to the interrupt service routine generally, through the interrupt vector , which contains the addresses of all the service routines Interrupt architecture must save the address of the interrupted instruction Incoming interrupts are disabled

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