CIT0623 - Chapter 1 Introduction PDF

Chapter 1: Introduction Objective  To describe the basic organization of computer systems  To provide a grand tour of the major components of operating systems  To give an overview of the many types of computing environments  To explore several open-source operating systems...

Chapter 1: Introduction Objective  To describe the basic organization of computer systems  To provide a grand tour of the major components of operating systems  To give an overview of the many types of computing environments  To explore several open-source operating systems  Contents  1.1 What Operating Systems Do?  1.2 Computer-System Organization  1.3 Computer-System Architecture  1.4 Operating-System Structure  1.5 Operating-System Operations  Operating System Software: 1.6 Process Management 1.7 Memory Management 1.8 Storage Management  1.9 Protection and Security  Categories of Operating Systems  1.11 Computing Environments  1.12 Open-Source Operating Systems  What is Operating System? A program that acts as an intermediary between a user of a computer and the computer hardware  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  Computer System Structure  Computer system can be divided into four components:  Hardware – provides basic computing resources  CPU, memory, I/O devices  Operating system  Controls and coordinates use of hardware among various applications and users  Application programs – define the ways in which the system resources are used to solve the computing problems of the users Word processors, compilers, web browsers, database systems, video games  Users People, machines, other computers 1.1 What Operating Systems Do  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. 1.1 What Operating Systems Do  An operating system is similar to a government. Like a government, it performs no useful function by itself. It simply provides an environment within which other programs can do useful work.  To understand more fully the operating system's role, we explore operating systems from two viewpoints:  The user  The system  1.1.1 User View  Single user computers (e.g., PC, workstations). Such systems are designed for one user to monopolize its resources. The goal is to maximize the work (or play) that the user is performing. the operating system is designed mostly for ease of use and good performance.  1.1.1 User View  Multi user computers (e.g., The main idea of developing a multi- mainframes, computing servers). user operating system is to use it for time-sharing and batch processing on These users share resources and mainframe computers. may exchange information. The operating system in such cases is designed to maximize resource utilization  to assure that all available CPU time, memory, and I/O are used efficiently and that no individual users takes more than their air share.  1.1.1 User View  Handheld computers (e.g., smartphones and tablets). The user interface for mobile computers generally features a touch screen. The systems are resource poor, optimized for usability and battery life.  1.1.1 User View  Embedded computers (e.g., computers in home devices and automobiles) The user interface may have numeric keypads and may turn indicator lights on or off to show status. The operating systems are designed primarily to run without user intervention.  Example: Android Auto, Apple CarPlay, Huawei HarmonyOS  1.1.2 System View  The operating system is a resource allocator  Manages all resources  Decides between conflicting requests for efficient and fair resource use  The operating systems is a control program Controls execution of programs to prevent errors and improper use of the computer  1.1.3 Defining OS  Operating systems exist to offer a reasonable way to solve the problem of creating a usable computing system.  The fundamental goal of computer systems is to execute user programs and to make solving user problems easier.  Since bare hardware alone is not particularly easy to use, application programs are developed.  These programs require certain common operations, such as those controlling the I/O devices.  The common functions of controlling and allocating resources are brought together into one piece of software: the  A simple viewpoint is that it includes everything a vendor ships when you order the operating system. The features that are included vary greatly across systems:  Some systems take up less than a megabyte of space and lack even a full-screen editor  Some systems require gigabytes of space and are based entirely on graphical windowing systems  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.  Application programs, which include all programs not associated with the operation of the system.  The emergence of mobile devices, have resulted in an increase in the number of features that constituting the operating 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.  For example, each of the two most prominent mobile operating systems -- Apple's iOS and Google's Android --feature a core kernel along with middleware that supports databases, multimedia, and graphics (to name only a few). 1.2 Computer-System Organization  Computer Startup  Bootstrap program is loaded at power-up or reboot  Typicallystored in ROM or EPROM, generally known as firmware  Initializes all aspects of system  Loads operating system kernel and starts execution  1.2.1 Computer-System Operation  Once the kernel is loaded and executing, it can start providing services to the system and its users.  Some services are provided outside of the kernel, by system programs that are loaded into memory at boot time to become system processes, or system daemons that run the entire time the kernel is running.  On UNIX, the first system process is init and it starts many other daemons. Once this phase is complete, the system is fully booted, and the system waits for some event to occur.  The occurrence of an event is usually signaled by an interrupt  1.3 Computer-System Architecture  Single general-purpose processor  Most systems have special-purpose processors as well  Multiprocessors systems growing in use and importance  Also known as parallel systems, tightly-coupled systems Advantages include: Increased throughput Economy of scale Increased reliability – graceful-degradation/fault- tolerance Two types: Symmetric Multiprocessing – each processor performs all tasks Asymmetric Multiprocessing – each processor is assigned a specific task. Asymmetric Multiprocessing Architecture Symmetric Multiprocessing Architecture  1.3.2 Multicore Systems  Most CPU design now includes multiple computing cores on a single chip. Such multiprocessor systems are termed multicore.  Multicore systems can be more efficient than multiple chips with single cores because:  On-chip communication is faster than between-chip communication.  One chip with multiple cores uses significantly less power than multiple single-core chips, an important issue for laptops as well as mobile devices.  Note -- while multicore systems are multiprocessor systems, not all multiprocessor systems are multicore.  Banyak tapak kaki boleh lari laju?  Boleh lari laju bermakna ada banyak kaki? 1.3.3 Clustered Systems Like multiprocessor systems, but multiple systems working together  Usually sharing storage via a storage-area network (SAN)  Provides a high-availability service which survives failures  Asymmetric clustering has one machine in hot-standby mode  Symmetric clustering has multiple nodes running applications, monitoring each other  Some clusters are for high-performance computing (HPC)  Applications must be written to use parallelization  Some have distributed lock manager (DLM) to avoid conflicting operations Clustered Systems  1.4 Operating-System Structure  Single user cannot always keep CPU and I/O devices busy  Multiprogramming organizes jobs (code and data) so CPU always has one to execute  A subset of total jobs in system is kept in memory  Batch systems:  One job selected and run via job scheduling  When it has to wait (for I/O for example), OS switches to another job  Timesharing systems:  Logical extension of batch systems -- CPU switches jobs so frequently that users can interact with each job while it is running, creating interactive computing Memory Layout for Multiprogramed System  Timesharing Systems  Timesharing is also referred to as multitasking.  Response time should be < 1 second  Each user has at least one program executing in memory.  Such a program is referred to as a process  If several processes are ready to run at the same time, we need to have CPU scheduling.  If processes do not fit in memory, swapping moves them in and out to run  Virtual memory allows execution of processes not completely in memory Watch for more infor  1. Multiprocessing Operating System https://youtu.be/IZfWjg3U3mA?si=uUySeasiS574YFVm  2. Batch Operating System https://youtu.be/sq2SE_GbZ34?si=Ov-YNSqXIdoIskN1  3. Multitasking Operating System https://youtu.be/fhhc_bjgiuA?si=sw4ooKTukt5NJwkC  4. Clustered System in OS https://youtu.be/E8WIIK0mxE8?si=0h9FEjd5Eh-FLqrg  5. What is an Operating System? Goals & Functions of Operating System https://youtu.be/ACsLvXuaKxw?si=JqPZ6c0bZJ0LW-LE