The document provides an introduction to operating system structures and operations. It discusses the basic components of a computer system including hardware, operating system, application programs, and users. It describes the functions of an operating system such as executing programs, managing system resources, and providing common services. The document also explains various operating system structures like memory layout, storage hierarchy, and system calls.
The objectives of these slides include -
- 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
The document provides an overview of operating system concepts, including:
- An operating system manages computer hardware and acts as an intermediary between users and the computer. It aims to execute programs, make the system convenient to use, and efficiently use hardware resources.
- A computer system consists of hardware, an operating system, application programs, and users. The operating system controls resource allocation and coordinates hardware, applications, and users.
- Operating systems provide services like file management, communication, error detection, resource allocation, accounting, and protection/security. System calls are the programming interface for these services.
The document provides an introduction to operating systems, describing their goals and functions. It discusses the components of a computer system including hardware, operating system, application programs, and users. It then describes what operating systems do from different perspectives, such as managing shared resources efficiently. The rest of the document outlines some key operating system concepts like process management, memory management, file system management, and how interrupts, multiprogramming, and multitasking work.
This chapter provides an introduction and overview of operating systems. It defines an operating system as a program that manages computer hardware and software resources and provides common services for computer programs. It describes the components of a computer system including hardware, operating system, application programs, and users. It then discusses the structure and functions of operating systems, including process management, memory management, storage management, protection and security, and distributed systems. It provides examples of different computing environments like traditional, client-server, peer-to-peer, and web-based computing.
This document provides an overview of operating systems, including definitions, functions, evolution, hardware components, structures, services, and system calls. It defines an operating system as a program that acts as an interface between the user and computer hardware, controlling program execution and important functions like memory management, I/O handling, and security. The document also outlines the major components of a computer system, different OS architectures, common OS services, and how system calls are used to request services from the kernel.
The objectives of these slides include -
- 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
The document provides an overview of operating system concepts, including:
- An operating system manages computer hardware and acts as an intermediary between users and the computer. It aims to execute programs, make the system convenient to use, and efficiently use hardware resources.
- A computer system consists of hardware, an operating system, application programs, and users. The operating system controls resource allocation and coordinates hardware, applications, and users.
- Operating systems provide services like file management, communication, error detection, resource allocation, accounting, and protection/security. System calls are the programming interface for these services.
The document provides an introduction to operating systems, describing their goals and functions. It discusses the components of a computer system including hardware, operating system, application programs, and users. It then describes what operating systems do from different perspectives, such as managing shared resources efficiently. The rest of the document outlines some key operating system concepts like process management, memory management, file system management, and how interrupts, multiprogramming, and multitasking work.
This chapter provides an introduction and overview of operating systems. It defines an operating system as a program that manages computer hardware and software resources and provides common services for computer programs. It describes the components of a computer system including hardware, operating system, application programs, and users. It then discusses the structure and functions of operating systems, including process management, memory management, storage management, protection and security, and distributed systems. It provides examples of different computing environments like traditional, client-server, peer-to-peer, and web-based computing.
This document provides an overview of operating systems, including definitions, functions, evolution, hardware components, structures, services, and system calls. It defines an operating system as a program that acts as an interface between the user and computer hardware, controlling program execution and important functions like memory management, I/O handling, and security. The document also outlines the major components of a computer system, different OS architectures, common OS services, and how system calls are used to request services from the kernel.
This document provides an overview of operating systems, including definitions, functions, evolution, hardware components, structures, services, and system calls. It defines an operating system as a program that acts as an interface between the user and computer hardware, controlling program execution and important functions like memory management, I/O handling, and security. The document also outlines the four generations of OS evolution and describes common OS components, architectures, and services including process management, file systems, communication, and resource allocation. Finally, it explains that system calls provide an interface for programs to request OS kernel services.
1. The document provides an introduction to operating systems, covering topics like computer system architecture, operating system structure and operations, types of computing environments, and operating system services.
2. It describes the basic components of an operating system including process management, memory management, storage management, I/O subsystem management, and protection and security.
3. Various computing environments are discussed, including stand-alone systems, distributed systems, client-server models, peer-to-peer networks, virtualization, cloud computing, and real-time embedded systems.
This document provides a summary of key topics covered in lecture materials on operating systems. It discusses the basic functions and components of operating systems including process management, memory management, CPU scheduling, synchronization, deadlocks, and virtual memory. Specific scheduling algorithms like first-come first-served, shortest job first and round-robin are explained. The document also covers operating system services, system calls, protection and various historical generations of operating systems.
This document provides an overview of operating system concepts. It begins by defining an operating system and describing its main functions, which include managing computer resources, establishing a user interface, and executing applications. It then discusses various operating system structures and operations, including interrupt handling, I/O structure, memory management, and processor management. The document concludes with an overview of the evolution of operating systems from simple batch systems to modern distributed computing environments.
This document outlines the structure and content of a course on operating system principles. It is divided into 5 units that cover topics like process management, memory management, distributed systems, and synchronization. The introduction defines key parts of a computer system like the operating system, hardware, and users. It describes the role of the operating system in allocating resources and controlling devices and programs. Examples are given of popular desktop, mobile, and server operating systems.
The document provides an overview of operating systems including:
- An operating system acts as an intermediary between the user and computer hardware to provide an environment for programs to execute, make the computer convenient to use, and allow efficient use of hardware.
- Operating systems control and coordinate the use of hardware resources among programs and users. They allocate resources like CPU time, memory, and I/O devices.
- Operating systems exist to make computing easier and more efficient by managing resources and controlling programs. They provide an interface between users, programs, and hardware.
The document provides an overview of operating system concepts and components. It defines an operating system as a program that acts as an intermediary between the computer hardware and the user. The key components of a computer system are described as the hardware, operating system, application programs, and users. The document outlines the basic functions of an operating system including managing processes, memory, storage, protection and security. It provides descriptions of computer system organization, interrupt handling, I/O structure, storage hierarchy and memory management. The structures of multiprogramming, timesharing and virtual memory systems are also summarized.
This document provides an introduction and overview of operating systems. It defines an operating system as a program that manages computer hardware resources and provides common services for computer programs. It describes the four main components of a computer system: hardware, operating system, application programs, and users. It also outlines some of the key services an operating system provides, such as program execution, I/O operations, file management, and resource allocation. Finally, it discusses the structure and evolution of modern operating systems from early batch and time-sharing systems to current multiprogramming systems.
The document provides an overview of operating systems, including definitions, functions, and evolution. Some key points:
- An operating system acts as an intermediary between user applications and computer hardware, managing resources and allowing for multitasking.
- The main functions of an OS include resource management, storage management, process management, memory management, file management, device management, and security/protection.
- Early operating systems evolved from serial processing to batch processing to multiprogramming and time-sharing to better utilize hardware and reduce turnaround time for users.
- Modern OS must balance individual usability, resource utilization, and response time depending on the system type (personal computer, mainframe, network, etc
The operating system provides programs an environment to execute and users services to run programs conveniently, including a user interface, program execution, I/O operations, file system manipulation, communication, error detection, and resource allocation. An operating system offers these services through system calls that programs make to request services from the kernel, while hiding the implementation details of system calls from programmers through an application programming interface. Key system calls include process creation, memory management, file access, device handling, protection, and networking.
The document provides an overview of operating system concepts, including definitions of an operating system, its functions, and different types of systems. It discusses mainframe systems using simple batch and multiprogramming operating systems. It also covers time-sharing/multitasking systems, desktop systems, and multiprocessor/parallel systems. The key functions of an operating system are described as process management, memory management, file management, device management, and security.
This document provides an introduction and overview of operating systems. It defines an operating system as a program that acts as an intermediary between the user and computer hardware to effectively utilize system resources and make problem solving easier. A computer system consists of hardware, operating system, application programs, and users. The operating system coordinates access to resources, executes programs, handles input/output, manages files and directories, and provides protection and security for multi-user systems. It discusses the evolution of operating systems and provides examples of early systems like batch processing and timesharing systems.
This document provides an overview of operating system concepts. It defines what an operating system is and its main functions. It describes different types of systems including serial processing, multiprogramming, time-sharing, parallel, distributed, real-time, desktop, handheld and embedded systems. It also covers operating system services, system calls, process management, memory management, secondary storage management, file systems management and I/O system management.
This document outlines the course content for an Operating Systems class divided into 5 units. Unit I introduces different types of operating systems like batch systems, time-sharing systems, personal computer systems, parallel systems, real-time systems, and distributed systems. It also covers system components, services, and structures. Unit II covers process management, CPU scheduling, and threads. Unit III discusses process synchronization, deadlocks, prevention and avoidance techniques. Unit IV covers memory management techniques like swapping, paging and segmentation as well as virtual memory. Unit V discusses file systems, file attributes, operations, structures and protection as well as mass storage structures.
operating systems concepts, ch-01, third level, Faculity of Applied Scinces, Seiyun University. انظمة التشغيل لطلاب المستوى الثالث بكلية العلوم التطبيقية المحاضرة 01
Advanced computer architecture lesson 1 and 2Ismail Mukiibi
An OS is a program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware. .....................
This document provides an introduction to operating systems. It defines an operating system as a program that acts as an intermediary between the user and computer hardware. The key components of a computer system are described as hardware, operating system, application programs, and users. Operating systems manage resources, control programs, and provide common services like memory management, process management, and I/O management. Various computing environments are explored, including traditional systems, mobile systems, distributed systems, client-server models, and virtualization.
This document contains lecture notes on operating systems. It covers topics like the definition and goals of operating systems, system components, processes and process states, CPU scheduling algorithms, synchronization between processes, deadlocks, memory management, and virtual memory. The key points are:
- An operating system acts as an intermediary between the user and computer hardware to provide an environment for running programs and efficiently using computer resources.
- System components include process management, memory management, file management, I/O management, networking, and protection.
- CPU scheduling algorithms like FCFS, SJF, priority, round-robin, and multilevel queue aim to make efficient use of CPU time between processes.
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
This document provides an overview of operating systems, including definitions, functions, evolution, hardware components, structures, services, and system calls. It defines an operating system as a program that acts as an interface between the user and computer hardware, controlling program execution and important functions like memory management, I/O handling, and security. The document also outlines the four generations of OS evolution and describes common OS components, architectures, and services including process management, file systems, communication, and resource allocation. Finally, it explains that system calls provide an interface for programs to request OS kernel services.
1. The document provides an introduction to operating systems, covering topics like computer system architecture, operating system structure and operations, types of computing environments, and operating system services.
2. It describes the basic components of an operating system including process management, memory management, storage management, I/O subsystem management, and protection and security.
3. Various computing environments are discussed, including stand-alone systems, distributed systems, client-server models, peer-to-peer networks, virtualization, cloud computing, and real-time embedded systems.
This document provides a summary of key topics covered in lecture materials on operating systems. It discusses the basic functions and components of operating systems including process management, memory management, CPU scheduling, synchronization, deadlocks, and virtual memory. Specific scheduling algorithms like first-come first-served, shortest job first and round-robin are explained. The document also covers operating system services, system calls, protection and various historical generations of operating systems.
This document provides an overview of operating system concepts. It begins by defining an operating system and describing its main functions, which include managing computer resources, establishing a user interface, and executing applications. It then discusses various operating system structures and operations, including interrupt handling, I/O structure, memory management, and processor management. The document concludes with an overview of the evolution of operating systems from simple batch systems to modern distributed computing environments.
This document outlines the structure and content of a course on operating system principles. It is divided into 5 units that cover topics like process management, memory management, distributed systems, and synchronization. The introduction defines key parts of a computer system like the operating system, hardware, and users. It describes the role of the operating system in allocating resources and controlling devices and programs. Examples are given of popular desktop, mobile, and server operating systems.
The document provides an overview of operating systems including:
- An operating system acts as an intermediary between the user and computer hardware to provide an environment for programs to execute, make the computer convenient to use, and allow efficient use of hardware.
- Operating systems control and coordinate the use of hardware resources among programs and users. They allocate resources like CPU time, memory, and I/O devices.
- Operating systems exist to make computing easier and more efficient by managing resources and controlling programs. They provide an interface between users, programs, and hardware.
The document provides an overview of operating system concepts and components. It defines an operating system as a program that acts as an intermediary between the computer hardware and the user. The key components of a computer system are described as the hardware, operating system, application programs, and users. The document outlines the basic functions of an operating system including managing processes, memory, storage, protection and security. It provides descriptions of computer system organization, interrupt handling, I/O structure, storage hierarchy and memory management. The structures of multiprogramming, timesharing and virtual memory systems are also summarized.
This document provides an introduction and overview of operating systems. It defines an operating system as a program that manages computer hardware resources and provides common services for computer programs. It describes the four main components of a computer system: hardware, operating system, application programs, and users. It also outlines some of the key services an operating system provides, such as program execution, I/O operations, file management, and resource allocation. Finally, it discusses the structure and evolution of modern operating systems from early batch and time-sharing systems to current multiprogramming systems.
The document provides an overview of operating systems, including definitions, functions, and evolution. Some key points:
- An operating system acts as an intermediary between user applications and computer hardware, managing resources and allowing for multitasking.
- The main functions of an OS include resource management, storage management, process management, memory management, file management, device management, and security/protection.
- Early operating systems evolved from serial processing to batch processing to multiprogramming and time-sharing to better utilize hardware and reduce turnaround time for users.
- Modern OS must balance individual usability, resource utilization, and response time depending on the system type (personal computer, mainframe, network, etc
The operating system provides programs an environment to execute and users services to run programs conveniently, including a user interface, program execution, I/O operations, file system manipulation, communication, error detection, and resource allocation. An operating system offers these services through system calls that programs make to request services from the kernel, while hiding the implementation details of system calls from programmers through an application programming interface. Key system calls include process creation, memory management, file access, device handling, protection, and networking.
The document provides an overview of operating system concepts, including definitions of an operating system, its functions, and different types of systems. It discusses mainframe systems using simple batch and multiprogramming operating systems. It also covers time-sharing/multitasking systems, desktop systems, and multiprocessor/parallel systems. The key functions of an operating system are described as process management, memory management, file management, device management, and security.
This document provides an introduction and overview of operating systems. It defines an operating system as a program that acts as an intermediary between the user and computer hardware to effectively utilize system resources and make problem solving easier. A computer system consists of hardware, operating system, application programs, and users. The operating system coordinates access to resources, executes programs, handles input/output, manages files and directories, and provides protection and security for multi-user systems. It discusses the evolution of operating systems and provides examples of early systems like batch processing and timesharing systems.
This document provides an overview of operating system concepts. It defines what an operating system is and its main functions. It describes different types of systems including serial processing, multiprogramming, time-sharing, parallel, distributed, real-time, desktop, handheld and embedded systems. It also covers operating system services, system calls, process management, memory management, secondary storage management, file systems management and I/O system management.
This document outlines the course content for an Operating Systems class divided into 5 units. Unit I introduces different types of operating systems like batch systems, time-sharing systems, personal computer systems, parallel systems, real-time systems, and distributed systems. It also covers system components, services, and structures. Unit II covers process management, CPU scheduling, and threads. Unit III discusses process synchronization, deadlocks, prevention and avoidance techniques. Unit IV covers memory management techniques like swapping, paging and segmentation as well as virtual memory. Unit V discusses file systems, file attributes, operations, structures and protection as well as mass storage structures.
operating systems concepts, ch-01, third level, Faculity of Applied Scinces, Seiyun University. انظمة التشغيل لطلاب المستوى الثالث بكلية العلوم التطبيقية المحاضرة 01
Advanced computer architecture lesson 1 and 2Ismail Mukiibi
An OS is a program that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware. .....................
This document provides an introduction to operating systems. It defines an operating system as a program that acts as an intermediary between the user and computer hardware. The key components of a computer system are described as hardware, operating system, application programs, and users. Operating systems manage resources, control programs, and provide common services like memory management, process management, and I/O management. Various computing environments are explored, including traditional systems, mobile systems, distributed systems, client-server models, and virtualization.
This document contains lecture notes on operating systems. It covers topics like the definition and goals of operating systems, system components, processes and process states, CPU scheduling algorithms, synchronization between processes, deadlocks, memory management, and virtual memory. The key points are:
- An operating system acts as an intermediary between the user and computer hardware to provide an environment for running programs and efficiently using computer resources.
- System components include process management, memory management, file management, I/O management, networking, and protection.
- CPU scheduling algorithms like FCFS, SJF, priority, round-robin, and multilevel queue aim to make efficient use of CPU time between processes.
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
Gender and Mental Health - Counselling and Family Therapy Applications and In...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 𝟏)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
𝐄𝐱𝐩𝐥𝐚𝐢𝐧 𝐭𝐡𝐞 𝐍𝐚𝐭𝐮𝐫𝐞 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐨𝐟 𝐚𝐧 𝐄𝐧𝐭𝐫𝐞𝐩𝐫𝐞𝐧𝐞𝐮𝐫:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
Walmart Business+ and Spark Good for Nonprofits.pdfTechSoup
"Learn about all the ways Walmart supports nonprofit organizations.
You will hear from Liz Willett, the Head of Nonprofits, and hear about what Walmart is doing to help nonprofits, including Walmart Business and Spark Good. Walmart Business+ is a new offer for nonprofits that offers discounts and also streamlines nonprofits order and expense tracking, saving time and money.
The webinar may also give some examples on how nonprofits can best leverage Walmart Business+.
The event will cover the following::
Walmart Business + (https://business.walmart.com/plus) is a new shopping experience for nonprofits, schools, and local business customers that connects an exclusive online shopping experience to stores. Benefits include free delivery and shipping, a 'Spend Analytics” feature, special discounts, deals and tax-exempt shopping.
Special TechSoup offer for a free 180 days membership, and up to $150 in discounts on eligible orders.
Spark Good (walmart.com/sparkgood) is a charitable platform that enables nonprofits to receive donations directly from customers and associates.
Answers about how you can do more with Walmart!"
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
हिंदी वर्णमाला पीपीटी, hindi alphabet PPT presentation, hindi varnamala PPT, Hindi Varnamala pdf, हिंदी स्वर, हिंदी व्यंजन, sikhiye hindi varnmala, dr. mulla adam ali, hindi language and literature, hindi alphabet with drawing, hindi alphabet pdf, hindi varnamala for childrens, hindi language, hindi varnamala practice for kids, https://www.drmullaadamali.com
Temple of Asclepius in Thrace. Excavation resultsKrassimira Luka
The temple and the sanctuary around were dedicated to Asklepios Zmidrenus. This name has been known since 1875 when an inscription dedicated to him was discovered in Rome. The inscription is dated in 227 AD and was left by soldiers originating from the city of Philippopolis (modern Plovdiv).
2. Unit I
Introduction: Operating Systems - Operating-System
Structure - Operating System operations. Operating System
Structures: Operating System Services - User and Operating
System Interface - System Calls - System Programs - Operating
System Design and Implementation - Operating System
Debugging- Operating System Generation - Types of
System Calls.
2
4. What is an 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
4
5. 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
5
6. Four Components of a Computer System
Figure 1. Four components of a Computer System
6
7. What Operating Systems Do?
• Depends on the point of view
• Users want convenience, ease of use and good performance
▫ Don’t care about resource utilization
• But shared computer such as mainframe or minicomputer must keep
all users happy
• Users of dedicate systems such as workstations have dedicated resources
but frequently use shared resources from servers
• Handheld computers are resource poor, optimized for usability and battery
life
• Some computers have little or no user interface, such as embedded
computers in devices and automobiles
7
8. Operating System Definition
• OS is a resource allocator
▫ Manages all resources
▫ Decides between conflicting requests for efficient and fair resource
use
• OS is a control program
▫ Controls execution of programs to prevent errors and improper use of
the computer
8
9. Operating System Definition (Cont.)
• No universally accepted definition
• “Everything a vendor ships when you order an operating system” is a
good approximation
▫ 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.
9
10. Computer Startup
• bootstrap program is loaded at power-up or reboot
▫ Typically stored in ROM or EPROM, generally known as firmware
▫ Initializes all aspects of system
▫ Loads operating system kernel and starts execution
10
11. Computer System Organization
• Computer-system operation
▫ One or more CPUs, device controllers connect through common bus
providing access to shared memory
▫ Concurrent execution of CPUs and devices competing for memory
cycles
Figure 2. Computer System Organization
11
12. Storage Structure
• Main memory – only large storage media that the CPU can access directly
▫ Random access
▫ Typically volatile
• Secondary storage – extension of main memory that provides large nonvolatile storage
capacity
• Hard disks – rigid metal or glass platters covered with magnetic recording material
▫ Disk surface is logically divided into tracks, which are subdivided into sectors
▫ The disk controller determines the logical interaction between the device and the
computer
• Solid-state disks – faster than hard disks, nonvolatile
▫ Various technologies
▫ Becoming more popular
12
13. Storage Hierarchy
• Storage systems organized in hierarchy
▫ Speed
▫ Cost
▫ Volatility
• Caching – copying information into faster storage system; main
memory can be viewed as a cache for secondary storage
• Device Driver for each device controller to manage I/O
▫ Provides uniform interface between controller and kernel
13
15. Operating System Structure
• Multiprogramming (Batch system) needed for efficiency
▫ Single user cannot keep CPU and I/O devices busy at all times
▫ Multiprogramming organizes jobs (code and data) so CPU always has one to execute
▫ A subset of total jobs in system is kept in memory
▫ One job selected and run via job scheduling
▫ When it has to wait (for I/O for example), OS switches to another job
• Timesharing (multitasking) is logical extension in which CPU switches jobs so frequently
that users can interact with each job while it is running, creating interactive computing
▫ Response time should be < 1 second
▫ Each user has at least one program executing in memory process
▫ If several jobs ready to run at the same time CPU scheduling
▫ If processes don’t fit in memory, swapping moves them in and out to run
▫ Virtual memory allows execution of processes not completely in memory
15
16. Memory Layout for Multi programmed System
Figure 9. Memory layout
16
17. Operating-System Operations
• Interrupt driven (hardware and software)
▫ Hardware interrupt by one of the devices
▫ Software interrupt (exception or trap):
Software error (e.g., division by zero)
Request for operating system service
Other process problems include infinite loop, processes modifying each other or
the operating system
17
18. Operating-System Operations (cont.)
• Dual-mode operation allows OS to protect itself and other system components
▫ User mode and kernel mode
▫ Mode bit provided by hardware
Provides ability to distinguish when system is running user code or kernel code
Some instructions designated as privileged, only executable in kernel mode
System call changes mode to kernel, return from call resets it to user
• Increasingly CPUs support multi-mode operations
▫ i.e. virtual machine manager (VMM) mode for guest VMs
18
19. Transition from User to Kernel Mode
• Timer to prevent infinite loop / process hogging resources
▫ Timer is set to interrupt the computer after some time period
▫ Keep a counter that is decremented by the physical clock.
▫ Operating system set the counter (privileged instruction)
▫ When counter zero generate an interrupt
▫ Set up before scheduling process to regain control or terminate program
that exceeds allotted time
Figure 10. Transition from user to Kernel mode
19
20. Activity
Case Study on Computer Operating System
Hint :MS-Windows, Ubuntu, Mac OS, Fedora,
Solaris, Free BSD, Chrome OS
22. Operating System Services
• Operating systems provide an environment for execution of programs and
services to programs and users
• One set of operating-system services provides functions that are helpful to
the user:
▫ User interface - Almost all operating systems have a user interface
(UI).
Varies between Command-Line (CLI), Graphics User Interface
(GUI), Batch
▫ Program execution - The system must be able to load a program into
memory and to run that program, end execution, either normally or
abnormally (indicating error)
▫ I/O operations - A running program may require I/O, which may
involve a file or an I/O device
22
23. Operating System Services (Cont.)
▫ File-system manipulation - The file system is of particular interest. Programs need to read
and write files and directories, create and delete them, search them, list file Information,
permission management.
▫ Communications – Processes may exchange information, on the same computer or between
computers over a network
Communications may be via shared memory or through message passing (packets moved by
the OS)
▫ Error detection – OS needs to be constantly aware of possible errors
May occur in the CPU and memory hardware, in I/O devices, in user program
For each type of error, OS should take the appropriate action to ensure correct and consistent
computing
Debugging facilities can greatly enhance the user’s and programmer’s abilities to efficiently use
the system
23
24. Operating System Services (Cont.)
• Another set of OS functions exists for ensuring the efficient operation of the system
itself via resource sharing
▫ Resource allocation - When multiple users or multiple jobs running
concurrently, resources must be allocated to each of them
Many types of resources - CPU cycles, main memory, file storage, I/O devices.
▫ Accounting - To keep track of which users use how much and what kinds of
computer resources
▫ Protection and security - The owners of information stored in a multiuser or
networked computer system may want to control use of that information,
concurrent processes should not interfere with each other
Protection involves ensuring that all access to system resources is controlled
Security of the system from outsiders requires user authentication, extends to
defending external I/O devices from invalid access attempts
24
25. A View of Operating System Services
Figure 15. View of OS
25
26. User and Operating System Interface - CLI
CLI or command interpreter allows direct command entry
▫ Sometimes implemented in kernel, sometimes by systems program
▫ Sometimes multiple flavors implemented – shells
▫ Primarily fetches a command from user and executes it
▫ Sometimes commands built-in, sometimes just names of programs
If the latter, adding new features doesn’t require shell modification
26
28. User and Operating System Interface - GUI
• User-friendly desktop metaphor interface
▫ Usually mouse, keyboard, and monitor
▫ Icons represent files, programs, actions, etc
▫ Various mouse buttons over objects in the interface cause various actions
(provide information, options, execute function, open directory (known as a
folder)
▫ Invented at Xerox PARC
• Many systems now include both CLI and GUI interfaces
▫ Microsoft Windows is GUI with CLI “command” shell
▫ Apple Mac OS X is “Aqua” GUI interface with UNIX kernel underneath and
shells available
▫ Unix and Linux have CLI with optional GUI interfaces (CDE, KDE(Kool
Desktop environment),GNOME(GNU Network Object Model Environment))
28
29. Touch screen Interfaces
n Touchscreen devices
require new interfaces
l Mouse not possible or not desired
l Actions and selection based on gestures
l Virtual keyboard for text entry
l Voice commands.
Figure 16. Touch screen Interfaces
29
30. The Mac OS X GUI
Figure 17.The max OS X GUI
30
31. System Calls
• Programming interface to the services provided by the OS
• Typically written in a high-level language (C or C++)
• Mostly accessed by programs via a high-level Application
Programming Interface (API) rather than direct system call use
• Three most common APIs are Win32 API for Windows, POSIX API for
POSIX-based systems (including virtually all versions of UNIX, Linux,
and Mac OS X), and Java API for the Java virtual machine (JVM)
31
32. Example of System Calls
• System call sequence to copy the contents of one file to another
file
Figure 18. Example of system calls
32
34. System Call Implementation
• Typically, a number associated with each system call
▫ System-call interface maintains a table indexed according to these
numbers
• The system call interface invokes the intended system call in OS
kernel and returns status of the system call and any return values
• The caller need know nothing about how the system call is
implemented
▫ Just needs to obey API and understand what OS will do as a result call
▫ Most details of OS interface hidden from programmer by API
Managed by run-time support library (set of functions built into libraries
included with compiler)
34
35. API – System Call – OS Relationship
Figure 20. API
35
36. System Call Parameter Passing
• Often, more information is required than simply identity of desired system
call
▫ Exact type and amount of information vary according to OS and call
• Three general methods used to pass parameters to the OS
▫ Simplest: pass the parameters in registers
In some cases, may be more parameters than registers
▫ Parameters stored in a block, or table, in memory, and address of block
passed as a parameter in a register
This approach taken by Linux and Solaris
▫ Parameters placed, or pushed, onto the stack by the program and
popped off the stack by the operating system
▫ Block and stack methods do not limit the number or length of parameters
being passed
36
38. Types of System Calls
• Process control
▫ create process, terminate process
▫ end, abort
▫ load, execute
▫ get process attributes, set process attributes
▫ wait for time
▫ wait event, signal event
▫ allocate and free memory
▫ Dump memory if error
▫ Debugger for determining bugs, single step
execution
▫ Locks for managing access to shared data between
processes
38
39. Types of System Calls
• File management
▫ create file, delete file
▫ open, close file
▫ read, write, reposition
▫ get and set file attributes
• Device management
▫ request device, release device
▫ read, write, reposition
▫ get device attributes, set device attributes
▫ logically attach or detach devices
39
40. Types of System Calls (Cont.)
• Information maintenance
▫ get time or date, set time or date
▫ get system data, set system data
▫ get and set process, file, or device attributes
• Communications
▫ create, delete communication connection
▫ send, receive messages if message passing model to host name or
process name
From client to server
▫ Shared-memory model create and gain access to memory regions
▫ transfer status information
▫ attach and detach remote devices
40
41. Types of System Calls (Cont.)
• Protection
▫ Control access to resources
▫ Get and set permissions
▫ Allow and deny user access
41
43. Standard C Library Example
• C program invoking printf() library call,
which calls write() system call
Figure 22. Standard C library Example
43
44. Example: MS-DOS
• Single-tasking
• Shell invoked when
system booted
• Simple method to run
program
▫ No process created
• Single memory space
• Loads program into
memory, overwriting
all but the kernel
• Program exit -> shell
reloaded At system startup running a program
44
45. Example: FreeBSD
• Unix variant
• Multitasking
• User login -> invoke user’s choice of
shell
• Shell executes fork() system call to
create process
▫ Executes exec() to load program into
process
▫ Shell waits for process to terminate or
continues with user commands
• Process exits with:
▫ code = 0 – no error
▫ code > 0 – error code
Figure 23. Free BSD
45
46. System Programs
• System programs provide a convenient environment for
program development and execution. They can be divided into:
▫ File manipulation
▫ Status information sometimes stored in a File modification
▫ Programming language support
▫ Program loading and execution
▫ Communications
▫ Background services
▫ Application programs
• Most users’ view of the operation system is defined by system
programs, not the actual system calls
46
47. System Programs
• Provide a convenient environment for program development and execution
▫ Some of them are simply user interfaces to system calls; others are considerably more complex
• File management - Create, delete, copy, rename, print, dump, list, and generally manipulate
files and directories
• Status information
▫ Some ask the system for info - date, time, amount of available memory, disk space, number of
users
▫ Others provide detailed performance, logging, and debugging information
▫ Typically, these programs format and print the output to the terminal or other output devices
▫ Some systems implement a registry - used to store and retrieve configuration information
47
48. System Programs (Cont.)
• File modification
▫ Text editors to create and modify files
▫ Special commands to search contents of files or perform transformations of the text
• Programming-language support - Compilers, assemblers, debuggers and
interpreters sometimes provided
• Program loading and execution- Absolute loaders, relocatable loaders, linkage
editors, and overlay-loaders, debugging systems for higher-level and machine language
• Communications - Provide the mechanism for creating virtual connections among
processes, users, and computer systems
▫ Allow users to send messages to one another’s screens, browse web pages, send
electronic-mail messages, log in remotely, transfer files from one machine to another
48
49. System Programs (Cont.)
• Background Services
▫ Launch at boot time
Some for system startup, then terminate
Some from system boot to shutdown
▫ Provide facilities like disk checking, process scheduling, error
logging, printing
▫ Run in user context not kernel context
▫ Known as services, subsystems, daemons
• Application programs
▫ Don’t pertain to system
▫ Run by users
▫ Not typically considered part of OS
▫ Launched by command line, mouse click, finger poke
49
50. Operating System Design and Implementation
• Design and Implementation of OS not “solvable”, but some approaches have
proven successful
• Internal structure of different Operating Systems can vary widely
• Start the design by defining goals and specifications
• Affected by choice of hardware, type of system
• User goals and System goals
▫ User goals – operating system should be convenient to use, easy to learn,
reliable, safe, and fast
▫ System goals – operating system should be easy to design, implement, and
maintain, as well as flexible, reliable, error-free, and efficient
50
51. Operating System Design and
Implementation (Cont.)
• Important principle to separate
Policy: What will be done?
Mechanism: How to do it?
• Mechanisms determine how to do something, policies decide
what will be done
• The separation of policy from mechanism is a very important
principle, it allows maximum flexibility if policy decisions
are to be changed later (example – timer)
• Specifying and designing an OS is highly creative task of
software engineering
51
52. Implementation
• Much variation
▫ Early OSes in assembly language
▫ Then system programming languages like Algol, PL/1
▫ Now C, C++
• Actually usually a mix of languages
▫ Lowest levels in assembly
▫ Main body in C
▫ Systems programs in C, C++, scripting languages like PERL,
Python, shell scripts
• More high-level language easier to port to other hardware
▫ But slower
• Emulation can allow an OS to run on non-native hardware
52
53. Operating System Structure
• General-purpose OS is very large
program
• Various ways to structure ones
▫ Simple structure – MS-DOS
▫ More complex -- UNIX
▫ Layered – an abstraction
▫ Microkernel -Mac
53
54. Simple Structure -- MS-DOS
• MS-DOS – written to
provide the most
functionality in the
least space
▫ Not divided into
modules
▫ Although MS-DOS has
some structure, its
interfaces and levels of
functionality are not
well separated Figure 24. Simple structure – MS DOS
54
55. Non Simple Structure --
UNIX
UNIX – limited by hardware functionality, the original
UNIX operating system had limited structuring. The UNIX
OS consists of two separable parts
▫ Systems programs
▫ The kernel
Consists of everything below the system-call interface and above
the physical hardware
Provides the file system, CPU scheduling, memory management,
and other operating-system functions; a large number of
functions for one level
55
56. Traditional UNIX System Structure
Beyond simple but not fully layered
Figure 25. Traditional UNIX System Structure
56
57. Layered Approach
• 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 Figure 26 . Layered Approach
57
58. Microkernel System Structure
• Moves as much from the kernel into user space
• Mach example of microkernel
▫ Mac OS X kernel (Darwin) partly based on Mach
• Communication takes place between user modules using
message passing
• Benefits:
▫ Easier to extend a microkernel
▫ Easier to port the operating system to new architectures
▫ More reliable (less code is running in kernel mode)
▫ More secure
• Detriments:
▫ Performance overhead of user space to kernel space communication
58
60. Modules
• Many modern operating systems implement loadable kernel
modules
▫ Uses object-oriented approach
▫ Each core component is separate
▫ Each talks to the others over known interfaces
▫ Each is loadable as needed within the kernel
• Overall, similar to layers but with more flexible
▫ Linux, Solaris, etc
60
62. Hybrid Systems
• Most modern operating systems are actually not one pure model
▫ Hybrid combines multiple approaches to address performance,
security, usability needs
▫ Linux and Solaris kernels in kernel address space, so monolithic,
plus modular for dynamic loading of functionality
▫ Windows mostly monolithic, plus microkernel for different
subsystem personalities
• Apple Mac OS X hybrid, layered, Aqua UI plus Cocoa
programming environment
▫ Below is kernel consisting of Mach microkernel and BSD Unix parts,
plus I/O kit and dynamically loadable modules (called kernel
extensions)
62
63. Mac OS X Structure
graphical user interface
Aqua
application environments and services
kernel environment
Java Cocoa Quicktime BSD
Mach
I/O kit kernel extensions
BSD
Figure 29. Mac OXS X Structure
63
64. iOS
• Apple mobile OS for iPhone, iPad
▫ Structured on Mac OS X, added
functionality
▫ Does not run OS X applications
natively
Also runs on different CPU
architecture (ARM vs. Intel)
▫ Cocoa Touch Objective-C API for
developing apps
▫ Media services layer for graphics,
audio, video
▫ Core services provides cloud
computing, databases
▫ Core operating system, based on Mac
OS X kernel
64
65. Android
• Developed by Open Handset Alliance (mostly Google)
▫ Open Source
• Similar stack to IOS
• Based on Linux kernel but modified
▫ Provides process, memory, device-driver management
▫ Adds power management
• Runtime environment includes core set of libraries
and Dalvik virtual machine
▫ Apps developed in Java plus Android API
Java class files compiled to Java bytecode then translated
to executable than runs in Dalvik VM
• Libraries include frameworks for web browser
(webkit), database (SQLite), multimedia, smaller libc
65
67. Operating-System Debugging
• Debugging is finding and fixing errors, or bugs
• OS generate log files containing error information
• Failure of an application can generate core dump file capturing
memory of the process
• Operating system failure can generate crash dump file containing
kernel memory
• Beyond crashes, performance tuning can optimize system performance
▫ Sometimes using trace listings of activities, recorded for analysis
▫ Profiling is periodic sampling of instruction pointer to look for statistical
trends
Kernighan’s Law: “Debugging is twice as hard as writing the code in the
first place. Therefore, if you write the code as cleverly as possible, you
are, by definition, not smart enough to debug it.”
67
68. Performance Tuning
• Improve
performance by
removing
bottlenecks
• OS must provide
means of
computing and
displaying
measures of
system behavior
• For example, “top”
program or
Windows Task
Manager
Figure 31. Performance Tuning
68
69. DTrace
DTrace tool in Solaris,
FreeBSD, Mac OS X allows
live instrumentation on
production systems
Probes fire when code is
executed within a
provider, capturing state
data and sending it to
consumers of those
probes
Example of following
XEventsQueued system call
move from libc library to
kernel and back
Figure 32. DTrace
69
70. Dtrace (Cont.)
DTrace code to record
amount of time each
process with UserID 101 is
in running mode (on CPU)
in nanoseconds
70
71. Operating System Generation
Operating systems are designed to run on any of a class of machines;
the system must be configured for each specific computer site
SYSGEN program obtains information concerning the specific
configuration of the hardware system
Used to build system-specific compiled kernel or system-tuned
Can general more efficient code than one general kernel
71