Chapter 1: Introduction Operating System Concepts – 9th Edit9on Silberschatz, Galvin and Gagne ©2013 Chapter 1: Introduction s What Operating Systems Do s Computer-System Organization s Computer-System Architecture s Operating-System Structure s Operating-System Operations s Process Management s Memory Management s Storage Management s Protection and Security s Kernel Data Structures s Computing Environments s Open-Source Operating Systems Operating System Concepts – 9th Edition 1.2 Silberschatz, Galvin and Gagne ©2013 Objectives s To describe the basic organization of computer systems s To provide a grand tour of the major components of operating systems s To give an overview of the many types of computing environments s To explore several open-source operating systems Operating System Concepts – 9th Edition 1.3 Silberschatz, Galvin and Gagne ©2013 What is an Operating System? s A program that acts as an intermediary between a user of a computer and the computer hardware s Operating system goals: q Execute user programs and make solving user problems easier q Make the computer system convenient to use q Use the computer hardware in an efficient manner Operating System Concepts – 9th Edition 1.4 Silberschatz, Galvin and Gagne ©2013 Computer System Structure s Computer system can be divided into four components: q Hardware – provides basic computing resources  q Operating system  q 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  q CPU, memory, I/O devices Word processors, compilers, web browsers, database systems, video games Users  People, machines, other computers Operating System Concepts – 9th Edition 1.5 Silberschatz, Galvin and Gagne ©2013 Four Components of a Computer System Operating System Concepts – 9th Edition 1.6 Silberschatz, Galvin and Gagne ©2013 What Operating Systems Do s Depends on the point of view s Users want convenience, ease of use q Don’t care about resource utilization s But shared computer such as mainframe or minicomputer must keep all users happy s Users of dedicate systems such as workstations have dedicated resources but frequently use shared resources from servers s Handheld computers are resource poor, optimized for usability and battery life s Some computers have little or no user interface, such as embedded computers in devices and automobiles Operating System Concepts – 9th Edition 1.7 Silberschatz, Galvin and Gagne ©2013 Operating System Definition s OS is a resource allocator q q s Manages all resources Decides between conflicting requests for efficient and fair resource use OS is a control program q Controls execution of programs to prevent errors and improper use of the computer Operating System Concepts – 9th Edition 1.8 Silberschatz, Galvin and Gagne ©2013 Operating System Definition (Cont.) s No universally accepted definition s “Everything a vendor ships when you order an operating system” is good approximation q s But varies wildly “The one program running at all times on the computer” is the kernel Everything else is either a system program (ships with the operating system) or an application program Operating System Concepts – 9th Edition 1.9 Silberschatz, Galvin and Gagne ©2013 Computer System Organization s Computer-system operation q One or more CPUs, device controllers connect through common bus providing access to shared memory q Concurrent execution of CPUs and devices competing for memory cycles Operating System Concepts – 9th Edition 1.10 Silberschatz, Galvin and Gagne ©2013 I/O Subsystem s One purpose of OS is to hide peculiarities of hardware devices from the user s I/O subsystem responsible for q Memory management of I/O including:  buffering (storing data temporarily while it is being transferred)  caching (storing parts of data in faster storage for performance)  spooling (the overlapping of output of one job with input of other jobs) q General device-driver interface q Drivers for specific hardware devices Operating System Concepts – 9th Edition 1.30 Silberschatz, Galvin and Gagne ©2013 Protection and Security s Protection – any mechanism for controlling access of processes or users to resources defined by the OS s Security – defense of the system against internal and external attacks q Huge range, including denial-of-service, worms, viruses, identity theft, theft of service s Systems generally first distinguish among users, to determine who can what q User identities (user IDs, security IDs) include name and associated number, one per user q User ID then associated with all files, processes of that user to determine access control q Group identifier (group ID) allows set of users to be defined and controls managed, then also associated with each process, file q Privilege escalation allows user to change to effective ID with more rights Operating System Concepts – 9th Edition 1.31 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Traditional s Stand-alone general purpose machines s But blurred as most systems interconnect with others (i.e the Internet) s Portals provide web access to internal systems s Network computers (thin clients) are like Web terminals s Mobile computers interconnect via wireless networks s Networking becoming ubiquitous – even home systems use firewalls to protect home computers from Internet attacks Operating System Concepts – 9th Edition 1.32 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Mobile s Handheld smartphones, tablets, etc s What is the functional difference between them and a “traditional” laptop? s Extra feature – more OS features (GPS, gyroscope) s Allows new types of apps like augmented reality s Use IEEE 802.11 wireless, or cellular data networks for connectivity s Leaders are Apple iOS and Google Android Operating System Concepts – 9th Edition 1.33 Silberschatz, Galvin and Gagne ©2013 Computing Environments – Distributed s Distributed q Collection of separate, possibly heterogeneous, systems networked together  Network is a communications path, TCP/IP most common – – Wide Area Network (WAN) – Metropolitan Area Network (MAN) – q Local Area Network (LAN) Personal Area Network (PAN) Network Operating System provides features between systems across network  Communication  Illusion scheme allows systems to exchange messages of a single system Operating System Concepts – 9th Edition 1.34 Silberschatz, Galvin and Gagne ©2013 Computing Environments – Client-Server s Client-Server Computing q Dumb terminals supplanted by smart PCs q Many systems now servers, responding to requests generated by clients  Compute-server system provides an interface to client to request services (i.e., database)  File-server system provides interface for clients to store and retrieve files Operating System Concepts – 9th Edition 1.35 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Peer-to-Peer s Another model of distributed system s P2P does not distinguish clients and servers q Instead all nodes are considered peers q May each act as client, server or both q Node must join P2P network   q Registers its service with central lookup service on network, or Broadcast request for service and respond to requests for service via discovery protocol Examples include Napster and Gnutella, Voice over IP (VoIP) such as Skype Operating System Concepts – 9th Edition 1.36 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Virtualization s Allows operating systems to run applications within other OSes q Vast and growing industry s Emulation used when source CPU type different from target type (i.e PowerPC to Intel x86) q Generally slowest method q When computer language not compiled to native code – Interpretation s Virtualization – OS natively compiled for CPU, running guest OSes also natively compiled q Consider VMware running WinXP guests, each running applications, all on native WinXP host OS q VMM provides virtualization services Operating System Concepts – 9th Edition 1.37 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Virtualization s Use cases involve laptops and desktops running multiple OSes for exploration or compatibility q Apple laptop running Mac OS X host, Windows as a guest q Developing apps for multiple OSes without having multiple systems q QA testing applications without having multiple systems q Executing and managing compute environments within data centers s VMM can run natively, in which case they are also the host q There is no general purpose host then (VMware ESX and Citrix XenServer) Operating System Concepts – 9th Edition 1.38 Silberschatz, Galvin and Gagne ©2013 Computing Environments - Virtualization Operating System Concepts – 9th Edition 1.39 Silberschatz, Galvin and Gagne ©2013 Computing Environments – Cloud Computing s Delivers computing, storage, even apps as a service across a network s Logical extension of virtualization as based on virtualization q Amazon EC2 has thousands of servers, millions of VMs, PBs of storage available across the Internet, pay based on usage s Many types q Public cloud – available via Internet to anyone willing to pay q Private cloud – run by a company for the company’s own use q Hybrid cloud – includes both public and private cloud components q Software as a Service (SaaS) – one or more applications available via the Internet (i.e word processor) q Platform as a Service (PaaS) – software stack ready for application use via the Internet (i.e a database server) q Infrastructure as a Service (IaaS) – servers or storage available over Internet (i.e storage available for backup use) Operating System Concepts – 9th Edition 1.40 Silberschatz, Galvin and Gagne ©2013 Computing Environments – Cloud Computing s Cloud compute environments composed of traditional OSes, plus VMMs, plus cloud management tools q Internet connectivity requires security like firewalls q Load balancers spread traffic across multiple applications Operating System Concepts – 9th Edition 1.41 Silberschatz, Galvin and Gagne ©2013 Computing Environments – Real-Time Embedded Systems s Real-time embedded systems most prevalent form of computers q Vary considerable, special purpose, limited purpose OS, real-time OS q Use expanding s Many other special computing environments as well q Some have OSes, some perform tasks without an OS s Real-time OS has well-defined fixed time constraints q Processing must be done within constraint q Correct operation only if constraints met Operating System Concepts – 9th Edition 1.42 Silberschatz, Galvin and Gagne ©2013 Open-Source Operating Systems s Operating systems made available in source-code format rather than just binary closed-source s Counter to the copy protection and Digital Rights Management (DRM) movement s Started by Free Software Foundation (FSF), which has “copyleft” GNU Public License (GPL) s Examples include GNU/Linux and BSD UNIX (including core of Mac OS X), and many more s Can use VMM like VMware Player (Free on Windows), Virtualbox (open source and free on many platforms http://www.virtualbox.com ) q Use to run guest operating systems for exploration Operating System Concepts – 9th Edition 1.43 Silberschatz, Galvin and Gagne ©2013 End of Chapter Operating System Concepts – 9th Edit9on Silberschatz, Galvin and Gagne ©2013