CS311-Lec1.pdfCS311-Lec1.pdfCS311-Lec1.pdf
- 1. Operating Systems Course Code: CS311 Instructor: Dr. Sarah Iqbal Lecture # 1 “Introduction to the Course”
- 2. LH 1 10:30 – 11:20 MONDAY LH 1 10:30 – 11:20 THURSDAY LH 1 10:30 – 11:20 FRIDAY Course Info. & Lecture Schedule • Course Pre-Requisite: CS221 Data Structures • Credit Hours: 3 Hrs. • Lecture Time and Venue: • Instructor: Dr. Sarah Iqbal Office: G-12 FCSE Lobby, GIK Institute sarah.iqbal@giki.edu.pk Office Hours: Tuesday 10:00 AM – 12:00 PM 2
- 3. Grading Policy 3 Weightage Assessment Items 10 % Quizzes 05 % Assignments 15 % Project & Presentations 30 % Mid Exam 40 % Final Exam
- 4. Text & Reference Books • Remzi H. Arpaci-Dusseau and Andrea C. Arpaci-Dusseau, “Operating Systems: Three Easy Pieces”, CreateSpace Independent Publishing Platform, 2018 • William Stallings "Operating Systems: Internals & Design Principles", 9th Ed., Prentice Hall, 2017 • A. Silberschatz, P. B. Galvin and G. Gagne, “Operating System Concepts, Internals & Design Principles”, 10th Ed., Wiley , 2021 4
- 5. Agenda for Today • Introduction and purpose of the course • Organization of a computer system • Purpose of a computer system—setting the stage for OS concepts and principles • Outline of topics to be discussed in the course • What is an operating system? 5
- 6. Computer System 1. Hardware : basic computing resources 2. Operating system: controls & coordinates 3. Applications programs 4. Users 6
- 7. Organization of a Computer System 7 A computer system can be divided roughly into four components: • The hardware—the central processing unit (CPU), the memory, and the input/output (I/O) devices—provides the basic computing resources for the system. • The application programs—such as word processors, spreadsheets, compilers, and web browsers—define the ways in which these resources are used to solve users’ computing problems. • The operating system controls the hardware and coordinates its use among the various application programs for the various users. We can also view a computer system as consisting of hardware, software, and data. The operating system provides the means for proper use of these resources in the operation of the computer system. • The Users — which includes people, machines or other computers.
- 8. Purpose of a Computer System • Computer systems consist of software and hardware that are combined to provide a tool to solve specific problems in an efficient manner (tools helps to develop a programs) • The fundamental goal of computer systems is to execute/run programs • Computer hardware is constructed toward this goal. But bare hardware alone is not easy to use so application programs are developed. • These programs require certain common operations, such as controlling the I/O devices • The common functions of controlling and allocating resources are then brought together into one piece of software: the operating system. 8
- 9. What is an Operating System • A more common definition, and the one that we usually follow, is that the operating system is the one program running at all times on the computer— usually called the kernel. • Along with the kernel, there are two other types of programs: system programs, which are associated with the operating system but are not necessarily part of the kernel, and application programs, which include all programs not associated with the operation of the system. • Mobile operating systems often include not only a core kernel but also middleware—a set of software frameworks that provide additional services to application developers. • In summary, for our purposes, the operating system includes the always running kernel, middleware frameworks that ease application development and provide features, and system programs that aid in managing the system while it is running. 9
- 10. What Happens When You Run a Program 10 • The primary purpose of a computer system is to generate executable program and execute them. The main issues involved in performing these tasks are as follows; 1. Storing an executable on a secondary storage device such as hard disk 2. Loading executable from disk into the main memory 3. Setting the CPU state appropriately so that the program execution could begin 4. Creating multiple cooperating processes, synchronizing their access to shared data and allowing them to communicate with each other
- 11. Required Services by the OS 11 • Manage secondary storage devices • Manage primary storage (Main memory management) • Manage processes (through CPU scheduling)
- 12. Course Outline Computer System Organization and Architecture Operating System Operations and Structure Interrupts Process Management Processes and threads—scheduling, concurrency, synchronization, etc. Mutual Exclusion Semaphores Deadlock The Memory Hierarchy, Memory Management, Secondary Storage Management Virtual Memory File System Security Issues 12
- 14. Computer System Organization Interrupts, traps, and software interrupts (UNIX signals) Hardware protection 14
- 15. Computer System Architecture Single-Processor Systems Multiprocessor Systems Clustered Systems 15
- 16. Operating System Operations Multiprogramming & Multitasking Dual-Mode & Multimode Operation Timer 16
- 17. Operating System Structures Operating system services System calls Semantics of system call execution Operating system structures (monolithic, microkernel-based, layered, virtual machines, DOS/Windows, UNIX/Linux) System design and implementation 17
- 18. Processes Process concept (process, states, attributes, etc.) Process scheduling (scheduler) Context switching (dispatcher) Operations on processes (creation, termination, signaling, suspend, foreground, background, etc.) Process management in UNIX (fork, wait, exec, exit, etc.) Sample code for UNIX/Linux process management Concurrent processes Interprocess communication (IPC) • IPC in UNIX/Linux (pipe, FIFO, socket, message queue, etc.) • Communication between UNIX/Linux processes (pipe, mkfifo, read, write, close, etc.) 18
- 19. CPU Scheduling • Basic concepts • Scheduling criteria • Scheduling triggers • Scheduling algorithms • UNIX System scheduling algorithm • Optimal scheduling • Algorithm evaluation 19
- 20. Process Synchronization • Basic concept • The Critical Section Problem • Software-based solutions—the Bakery Algorithm • Hardware-based solutions • Semaphores • Classic problems of synchronization • Deadlocks and starvation • Critical regions • Monitors • Synchronization tools used in Linux, and Windows 20
- 21. Threads • Thread concept (thread, states, attributes, etc.) • Thread communication issues • Interthread Communication • Thread Synchronization • User- and kernel-level threads • POSIX threads (the pthread library) 21
- 22. Deadlocks • Basic concept • Deadlock characterization • Deadlock handling (prevention, avoidance, detection and recovery) • Banker’s algorithm 22
- 23. Memory Management • Basic concepts • Various techniques for memory management • Logical to physical address translation • Swapping • External fragmentation • Paging • Hardware support for paging • Internal fragmentation • Performance of paging • Protection and sharing • Page table issues: Multi-level paging, Hashed page tables, Inverted page tables • Segmentation • Segmentation with paging 23
- 24. File-System Management • Basic concepts (file attributes, operations, types, structure, etc.) • Access methods (sequential, random, etc.) • UNIX/Linux directory structure (links in UNIX) • File system mounting, sharing, and protection • UNIX/Linux examples for sharing and protection, and relevant commands (chmod, ln, ln –s, etc.) • Directory implementation • Free space management methods • Space Allocation Methods • Time and space performance of allocation methods 24
- 25. Mass Storage Structure and Scheduling • Disk structure and scheduling • Disk management (formatting, boot block etc.) 25
- 26. Virtual Memory • Basic concept • Demand paging • Page fault • Performance of demand paging • Page replacement • Allocation of frames • Thrashing • Operating-system examples 26
- 27. Two Viewpoints 27 User View • it varies according to the interface being used. • a laptop or a PC is designed for one user to monopolize its resources. In this case, the OS is designed mostly for ease of use, with some attention paid to performance and security and none paid to resource utilization. • many users interact with mobile devices such as smartphones and tablets—features a touch screen and many mobile devices also allow users to interact through a voice recognition interface. • Some computers have little or no user view. For example, embedded computers in home devices and automobiles but they and their operating systems and applications are designed primarily to run without user intervention.
- 28. Two Viewpoints… 28 System View • From the computer’s point of view, the operating system is the program most intimately involved with the hardware. • In this context, we can view an operating system as a resource allocator or a manager of these resources. Facing numerous and possibly conflicting requests for resources. • The operating system must decide how to allocate them to specific programs and users so that it can operate the computer system efficiently and fairly. • A slightly different view of an operating system emphasizes the need to control the various I/O devices and user programs. • An operating system is a control program. A control program manages the execution of user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.
- 29. What is an Operating System? • A program that acts as an intermediary between a user of a computer and the computer hardware—provides the user a simpler (virtual) machine to work with • A program that allocates and deallocates computer system resources in an efficient, fair, and secure manner—a resource manager 29 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.
- 30. Reference & Reading Material • Operating Systems Concepts, Chapter 1 30