No. 1 Introduction Operating Systems’ Concepts and Structure

No. 2 Books A. Silberschatz, P. B. Galvin, and G. Gagne, “Operating Systems Concepts (Essentials)”, 9th Edition, John Wiley & Sons, 2012 Andrew Tannenbaum, “Modern Operating Systems”, second edition, Prentice Hall,, 4th ed, Pearson, W. Stallings, “Operating Systems: Internals and Design Principles”, 8 th ed, Pearson,

No. 3 Contents Definition of an Operating System (OS) Role of an Operating System Classification of Operating Systems Specific terms and concepts

No. 4 A computer system consists of : User software System software Hardware Spring, 2008 End User Programmer Operating- System Designer Computer Hardware Operating-System Utilities Application Programs

No. 5 During our day to day work, we schedule Which one is urgent, E.g. while attending a Telephone call some other task also came in, now we have to decide and mange the tasks according to need. Similarly, OS is a manager manages the resources. The list of resources in a computer system are: 1 st resource is CPU User writes a program in a high level language and stored in the HDD of a system. CPU has no direct access to HDD, so it should go through the main memory 2 nd resource is main memory

No. 6 In order to process a data use secondary storage 3 rd resource is secondary storage 4 th resources are FDD, CDROM etc User write a program using key board and to get some thing as output from printer for hard copy or VDU for display. 5 th resource is I/O devices Responsibility of OS is now to manage more than one user/client, so that resources can be simultaneously managed.

No. 7 Distributed Systems In a situation where multiple independent computers are interconnected then we say Network + independent computers forms a distributed computing systems Having isolated computers Each is a computer having its own CPU, RAM, etc. An OS supporting networks is installed on them.

No. 8 OS as a Resource Manager Not in isolation. They must be in a distributed environment and can Cater the needs of users Mange the resources Thus we say Os can be considered as resource manager whose major responsibility is to manage the resources in such a way that all the clients of the system can make use of those resources in an efficient manner

No. 9 OS as a Resource Manager OS being a program can never be more powerful than us Code should be executable CPU Management or process management is the most important objective of our study

No. 10 The Definition of an OS A system software. A collection of procedures that manage all the system’s hardware resources and provide the users the environment in which they can use the system resources and run their own applications An OS provides services for Processor Management Memory Management File Management Device Management Concurrency Control

No. 11 The GOAL OF AN OS The primary objective of a computer is to execute an instruction in an efficient manner and to increase the productivity of processing resources attached with the computer system such as hardware resources, software resources and the users. In other words, we can say that maximum CPU utilisation is the main objective, because it is the main device which is to be used for the execution of the programs or instructions. We can brief the goals as: The primary goal of an operating system is to make the computer convenient to use. The secondary goal is to use the hardware in an efficient manner.

No. 12 Specific Terms and Concepts Batch systems: No user interaction Multiprogramming: Multiple programs loaded in memory Time-sharing: Each process receives slices of CPU time Interactive systems: Provides quick response to user’s actions Multi-user: Distinction between users Network OS: Users aware of the existence of multiple computers Distributed OS: Looks like a traditional single-processor system Real-time Systems: Correct system function depends on timeliness

No. 13 Types of OS 1. Batch Processing 2. Multi Programming 3. Time Sharing 4. Multi Tasking 5. Multi Processing 6. Distributed Processing 7. Network OS

No. 14 Examples of OS Mainframe operating systems: OS/390 Server operating systems : UNIX,Windows 2000,Linux Multiprocessor operating systems PC operating systems: Windows 98, Windows ME, Macintosh, Linux Real-time operating systems: VxWorks, QNX Embedded operating systems: PalmOS, Windows CE, Windows Mobile, Symbia

No. 15 Computer Hardware (1) An OS is closely tied to the HW it runs on HW components –CPU –Memory –I/O devices Monitor Keyboard Storage devices (HDD, Floppy etc.) Others –BUSes

No. 16 Computer Hardware (2) Monitor BUS

No. 17 Processor(CPU) processor

No. 18 CPU Functionality –fetch instructions from memory, decode and execute them Instruction set –has a specific set of instructions that can be executed –specific executable programs each processor can run Registers Program counter Stack pointer Many others – architecture dependent Machine state – saved at context switch Kernel vs. User mode of execution –switches between system calls hardware exceptions, interruptions

No. 19 Memory RAM

No. 20 Memory Should be extremely fast, large and cheap Hierarchy of layers –Registers: fastest, no delay, but limited size –Cache memory cache hits and misses –Main memory – RAM (Random Access Memory) –HDDs 2 orders of magnitude cheaper and larger then RAM, but 3 orders of magnitude slower mechanical device – heads, tracks (cylinders), sectors, –Magnetic tapes used as a backup for very large data sets very slow, but very cheap and removable

No. 21 I/O Devices Components –Controller and the device itself Controller –Directly controls the physical device –Receives commands from the OS Device driver –Supplied by controller manufacturer –Inserted into the OS – run in kernel mode Functionality –Busy waiting –Interrupts

No. 22 Processes Definition A program in execution Consists of: executable code, data, stack, CPU registers value, and other information A process hierarchy (tree) A created two child processes: B and C B created three child processes: D, E, and F Process synchronization Inter-Process Communication (IPC)

No. 23 Files Definition A collection of related information An abstraction of data stored on HDD A process tree File system mounting File linking

No. 24 Process manager: c reates, schedules and destroy processes Memory manager: a llocates and releases memory Disk manager I/O devices manager File system: c reate, read, modify, remove etc. files Communication system Protection system Shells text interface – command interpreter graphical interface The Structure of an OS Components

No Distributed Systems Distribute computation among many processors. Loosely coupled - –no shared memory, various communication lines client/server architectures Advantages: –resource sharing –computation speed-up –reliability –communication - e.g. Applications - digital libraries, digital multimedia Hardware – very cheap ; Human – very expensive

No Real-time systems Correct system function depends on timeliness Feedback/control loops Sensors and actuators Hard real-time systems – Failure if response time too long. Secondary storage is limited Soft real-time systems - Less accurate if response time is too long. Useful in applications such as multimedia, virtual reality.

No. 27 Objective 1.Which one is not a computer resource? 2.CPU has direct access to a) HDD b) Main memory c)Printer d) all the above 3. Os can function for a)Resource Management b) Processor Management c) Memory Management d) Device Management 4. The main purpose of OS is a)An environment to execute programs b)Manage computer resources c)Both (a) &(b) d) None of these a) Utilitiesb) OSc) System SWd) programmer

No. 28 Objective 5.The goal of an OS is a)Efficient CPU utilization b)Make the computer convenient to use c)Use of Hardware in a convenient manner d)Efficient net work communication 6. Windows 2000 is a a) PC OS b)Server OS c)RTOS d) Embeded 7. When each process receives slices of CPU time is a a)Multiprogramming OS b) Distributed OS c)Time-sharing OS d) RTOS 8.Which is a Random Access Memory a)HDD b)Registers c) FDD d) All the above

No. 29 Objective dbacabcbca 9.Which one is not an I/O device a)Controller b) Device driver c) RAM d) HDD 10. A program in execution is called a) Process b) process tree c) process synchronization d) All the above Answer