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  • 1. HASSAN BIN ALI Department of IT & Communication Politeknik Tuanku Syed SirajuddinFP202 Fundamental Of Operating System
  • 2.  At the end of this chapter, student will be able to:1) Define operating system2) List the use of operating system in computer system3) Describe various OS architecture4) Describe various types of OS FP202 Fundamental Of Operating System
  • 3.  Software program that controls the hardware. Definition of an operating system can be seen in four aspects:1) A group of program that acts as an intermediary between user, software and computer hardware.2) Controls and co-ordinates the use of computer resources among various application programs and user.3) Acts as a manager4) Allow the program to communicate with one another FP202 Fundamental Of Operating System
  • 4.  Basically, two types of software available:1) System software - Groups of program that control the hardware Systems software includes compilers,loaders, linkers, and  debuggers.2) Application software - Groups of programs that used by the end-user for various applications such as text processing, spreadsheet, etc OS categorized as system software - Build to act as an intermediary between user of a computer and computer hardware - Goal: Provide convenient and efficient environment for the user FP202 Fundamental Of Operating System
  • 5. User1 User2 User3 System and application programs Operating system HardwareFigure 1: Abstract view of the components of a computer system FP202 Fundamental Of Operating System
  • 6.  Functions OS:1) Resource Sharing- The OS contains a set of algorithms that allocates resources to the programs executed on behalf of the user.- These resources include time, power, hardware, etc...2) Control Program Controls the operation of the application programs to prevent errors affecting other programs.3) Provision of a Virtual Machine This hides interfaces to I/O devices, filing systems, etc, and provides a programming interface for applications.4) Kernel The kernel is the only program resident all the time (all other applications are application programs). FP202 Fundamental Of Operating System
  • 7.  OS has three objectives:1) Convenience - An OS make a computer more convenient to be used2) Efficiency - An OS allows the computer system resources to be used in an efficient manner3) Ability to evolve - An OS is constructed in such a way to as to permit the effective development, testing and introduction of new system function without at the same time interfering with service. FP202 Fundamental Of Operating System
  • 8. OPERATING SYSTEMARCHITECTURE FP202 Fundamental Of Operating System
  • 9.  This approach well known as “The Big Mess” - there is no structure. All kernel routines are together, any can call any A system call interface (main program, sys calls, utility functions) Examples: Linux, BSD Unix, Windows Pros 1) Shared kernel space 2) Good performance Cons 1) No information hiding 2) Inflexible 3) Chaotic 4) Difficult to understand FP202 Fundamental Of Operating System
  • 10.  The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface. With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers. Hiding information at each layer E.g. level 1 is processor allocation, level 1 memory management, level 2 communication, level 3 I/O, etc. Examples: THE System (6 layers), MS-DOS (4 layers) Pros 1) Layered abstraction 2) Separation of concerns, elegance Cons 1) Protection, boundary crossings FP202 Fundamental Of Operating System
  • 11.  The advent of new concepts in OS design, microkernel is aimed at migrating services of an operating system out of monolithic kernel into user level process. Divide the OS into several processes, each which implements a single set of services - Example: I/O servers, memory server, process server Each server runs in user mode, provide services to the requested client. Client: Another operating system component or application program, request service by sending message to server An OS kernel (microkernel) running in kernel mode deliver message to the server. The server perform operation, and microkernel delivers the result to client in another message. FP202 Fundamental Of Operating System
  • 12.  Components above microkernel communicate directly with one another, although using message that pass through the microkernel itself. Microkernel validate messages, passes them between the components and grants access to hardware. Example: C-DAC microkernel, Mach, Windows NT, Chorus FP202 Fundamental Of Operating System
  • 13. ……….Client-server model or microkernel FP202 Fundamental Of Operating System
  • 14. Example: Windows NT  Various applications (Win32, OS/2, and POSIX) run in user space.  Server for each application runs in user space.  Message passing between client application programs and application servers runs in kernel space. FP202 Fundamental Of Operating System
  • 15. OPERATINGSYSTEM TYPES
  • 16.  A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention. The basic physical layout of the memory of a batch job computer is shown below: Monitor (permanently resident) User Space- The monitor is system software that is responsible for interpreting (compilers, programs, data, and carrying out the instructions in the batch jobs. etc.)- When the monitor starts a job, the entire computer is dedicated to the job, which then controls the computer until it finishes.
  • 17.  Advantages: 1)Move much of the work of the operator to the computer 2)Increased performance since it was possible for job to start as soon as the previous job finished Disadvantages: 1)Due to lack of protection scheme, one batch job can affect pending jobs (read too many cards, etc) Example: A job could corrupt the monitor, thus affecting pending jobs 2)A job could enter an infinite loop
  • 18.  As machines with more and more memory became available, it was possible to extend the idea of multiprogramming (or multiprocessing) as used in batch systems. This create a systems that would load several jobs into memory at once and cycle through them in some order, working on each one for a specified period of time. The basic physical layout of a multiprogramming system is as shown: Monitor (more like an operating system) User program 1 User program 2 User program 3 User program 4
  • 19.  At this point the monitor is growing to the point where it begins to resemble a modern operating system. It is responsible for: 1)Starting user jobs 2)Spooling operations 3)IO for user jobs 4) Switching between user jobs 5) Ensuring proper protection while doing the above
  • 20.  There are different type of Multiprogramming Operating System such as:1) Multitasking Operating System A type of multiprogramming operating system which can perform several process simultaneously. The earliest multitasking OS available to home users was the AmigaOS. All current major operating system support this feature.
  • 21. 2) Multi-user Operating System A multi-user operating system allows for multiple users to use the same process at the same time and/or different times. Linux, Unix,Windows OS are some example of multitasking operating system.3) Multiprocessing Operating System An operating system capable of supporting and utilizing more than one computer.
  • 22. 4) Real Time Operating System Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Well-defined fixed-time constraints.
  • 23.  The Distributed Operating System is one that runs on multiple, autonomous CPUs which provides its users an illusion of an ordinary Centralized Operating System that runs on a virtual Uniprocessor. Distributed Operating System provide resource tranparency to the users processes. “If you can tell which computer you are using, you are not using a distributed system ” - Tanenbaum
  • 24. w o rks t a t io n s a lo c a l n e t w o r k T h e In te rn e t a n e tw o rk h o s t Distributed Operating System FP202 Fundamental Of Operating System
  • 25.  Advantages: 1)Price/Performance advantage (Availability of cheap and powerful Microprocessors). 2)Resources Sharing 3)Computation speed up – load sharing 4)Reliability and Availability. 5)Provides Transparency. Disadvantages: 1)Lack of security - Easy access also applies to secret data.
  • 26.  An example of a distributed system: Amoeba- An open source microkernel-based distributed operating system developed by Andrew S. Tanenbaum and others at the Vrije Universiteit.- The aim of the Amoeba project is to build a timesharing system that makes an entire network of computers appear to the user as a single machine.- Development seems to have stalled: the files in the latest version (5.3) were last modified on 12 February 2001.- Amoeba runs on several platforms, including i386, i486, 68030, Sun 3/50 and Sun 3/60.