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  1. Connecting with Computer Science, 2e Chapter 9 Operating Systems

  2. Objectives • In this chapter you will: • Learn what an operating system is • Become familiar with different types of operating systems • Identify the major functions of an operating system • Understand how operating systems manage processes Connecting with Computer Science, 2e

  3. Objectives (cont’d.) • In this chapter you will (cont’d.): • Understand how operating systems manage resources • Understand how operating systems provide security • Learn how to perform basic operating system file management functions in Windows and Linux Connecting with Computer Science, 2e

  4. Why You Need to Know About...Operating Systems • Operating system (OS) • Essential to the functioning of computers • Controls operations inside the computer • Operating system knowledge • Improves efficiency Connecting with Computer Science, 2e

  5. What Is an Operating System? • Program responsible for managing the user interface, system resources, and processes • Software control center • Loaded when computer boots • Resident in main memory • Loads and supervises all other programs • Provides interface to CPU and I/O devices • Capable of connecting with standard devices • Written in programming languages: C and C++ Connecting with Computer Science, 2e

  6. What Is an Operating System? (cont’d.) Figure 9-1, An OS provides an interface between the user, applications, and hardware Connecting with Computer Science, 2e

  7. What Is an Operating System? (cont’d.) • Parts: • Kernel: core program loaded at boot time by BIOS • Small program • Remains in memory the entire time the computer is on • Modules: provide user and device interface • Main module responsible for user interface • Windows: provides graphical desktop • Linux: Gnome, KDE, or Xfce graphical interface • Drivers interface with I/O devices • Loaded onto computer’s hard disk or ROM chip Connecting with Computer Science, 2e

  8. What Is an Operating System? (cont’d.) Figure 9-2, Users and computer components interact with the OS kernel Connecting with Computer Science, 2e

  9. What Is an Operating System? (cont’d.) • Microsoft Windows • Most widely used OS • Disk Operating System (DOS) • Predecessor to Windows • Linux or UNIX is used on many servers • Macintosh is used in schools • OS running on a computer is called a platform • OS fitted to a particular CPU • Cross-platform application runs on multiple platforms Connecting with Computer Science, 2e

  10. What Is an Operating System? (cont’d.) Table 9-1, OS development summary Connecting with Computer Science, 2e

  11. What Is an Operating System? (cont’d.) Table 9-1, OS development summary (cont’d.) Connecting with Computer Science, 2e

  12. What Is an Operating System? (cont’d.) Table 9-1, OS development summary (cont’d.) Connecting with Computer Science, 2e

  13. Types of Operating Systems • Classified by features or intended uses • Single-tasking: DOS and Windows 3.x • Allows running only one process (task) at a time • Multitasking: Windows, Linux, and Mac OS • Supports more than one process running at a time • Network operating systems (NOS): NetWare, UNIX, Linux, and Windows Server 2008 • Designed to provide strong network services • Multiprocessing • Coordinated execution of a process, using two or more CPUs at the same time Connecting with Computer Science, 2e

  14. Types of Operating Systems (cont’d.) • Each OS is designed to be strong in a particular area • Microsoft Windows and Mac OS • Appeal to home and small-business users • Installed on the overwhelming majority of desktops • UNIX and Linux • Strong in multitasking, security, and multiprocessing • Known for stability • Server environment operating systems • Many other OSs run on PDAs and cell phones Connecting with Computer Science, 2e

  15. Functions of an Operating System • Basic functions • Provide a user interface • Schedule and manage program execution • Manage memory • Configure devices • Provide file management and security • Provide basic networking capability • Monitor performance Connecting with Computer Science, 2e

  16. Functions of an Operating System (cont’d.) • Four main categories • Providing a user interface • Managing processes • Managing resources (including memory) • Providing security Connecting with Computer Science, 2e

  17. Providing a User Interface • User interface • Program enabling computer communication • DOS and Linux use a command-line interface • Sometimes called console operating systems • Command-line interface • Type commands and receive responses in text format • Command prompt • Words and symbols displayed onscreen that indicate the OS is waiting for user input Connecting with Computer Science, 2e

  18. Providing a User Interface (cont’d.) • Graphical user interface (GUI) • Information displayed in a graphical format • User can select items using a pointing device (e.g., mouse) • Clicking icons and buttons opens graphical windows and allows menu selections Connecting with Computer Science, 2e

  19. Providing a User Interface (cont’d.) Figure 9-3, The Windows command prompt emulates a DOS environment (top); the default GUI interface of Windows Vista (middle); and the GUI interface of Linux (bottom) Connecting with Computer Science, 2e

  20. Providing a User Interface (cont’d.) Figure 9-3, (cont’d.) Connecting with Computer Science, 2e

  21. Providing a User Interface (cont’d.) • Windows command prompt access • Access at: All Programs, Accessories menu • Emulates a DOS environment • Provides backward compatibility • GUIs can be added to Linux • Standard Linux uses command-line interface Connecting with Computer Science, 2e

  22. Managing Processes • Operating system responsibilities • Loads, starts, supervises, and stops processes • Process • Each program running on a computer • May start (spawn) other processes to support them • Windows Task Manager shows running processes • Accessed by pressing Ctrl+Alt+Delete keys • Linux displays information on active processes • Use the ps command • DOS currently has no command to list processes Connecting with Computer Science, 2e

  23. Managing Processes (cont’d.) Figure 9-4, Windows Task Manager Connecting with Computer Science, 2e

  24. Managing Processes (cont’d.) Figure 9-5, Viewing processes in Linux with the ps command Connecting with Computer Science, 2e

  25. Managing Processes (cont’d.) • CPUs only run one process at a time • Von Neumann architecture supports serial execution • Only one instruction from one single program per clock cycle allowed • Differences in component speed • Allows CPU to execute extra instructions • CPU executes billions of instructions per second • Memory, keyboard, monitor, and network adapter function at different speeds • CPU multitasks while waiting Connecting with Computer Science, 2e

  26. Managing Processes (cont’d.) • Time slicing • Allows multiple processes to share the CPU • Provides illusion of simultaneous execution • Attributable to the different speeds of devices • Managed by the OS • Complicated task • Uses interrupt handling • Allows processes to interrupt the CPU • Interrupts initiated by programs or devices • Main interrupt handler: part of the OS Connecting with Computer Science, 2e

  27. Managing Resources • Devices connected to the CPU • Main memory, hard disk, and CD/DVD-ROM drive • All running processes share these devices • Configure I/O devices within environment • Plug and Play (PnP) automates process (from 1995) • Relieves manual jumper and switch setting • Deadlock • Resources freeze system • OS must remedy or system will need rebooting Connecting with Computer Science, 2e

  28. Managing Memory • OS manages memory • Determines location of free space in memory • Loads programs from disk to this memory location • Constantly manages memory • Communicates with CPU about where to begin executing a program Connecting with Computer Science, 2e

  29. Providing Security • OS protects memory and other resources • Ensures resources distributed evenly among competing processes • Provides a means for allowing only authorized users to access programs or devices • Methods • Set up password-protected user accounts • Set up group policies • Govern resources a class or group of users allowed to access Connecting with Computer Science, 2e

  30. Using an Operating System • It is helpful to understand: • How an OS works • How to perform basic tasks • Skills focus: • Basic file management tasks Connecting with Computer Science, 2e

  31. Managing Disk Files • OS file organization • Folder or directory • Treelike structure • Single root level and one or more branches • Files viewed as leaves (nodes) on the tree structure • Command-line operating systems: • Linux and DOS • Similar structure used • Cannot view it as a tree structure • Windows Explorer • Manages files through graphical interface Connecting with Computer Science, 2e

  32. Managing Disk Files (cont’d.) Figure 9-6, The Windows interface for working with files and folders Connecting with Computer Science, 2e

  33. Managing Disk Files (cont’d.) Figure 9-7, Linux command-line interface for displaying files and folders Connecting with Computer Science, 2e

  34. Partitioning Disks • Before a disk can be used, it must be divided into partitions and formatted • Partitioning: dividing surface into specific areas (partitions) • Windows and Linux use the fdisk command • Linux: case sensitive • Windows: not case sensitive Connecting with Computer Science, 2e

  35. Formatting Disks • After a disk has been partitioned, it can be formatted • Arranges disk surface into addressable areas • Sets up basic directory tree structure • Places copy of the OS on the disk • Used as a boot disk for starting the computer Connecting with Computer Science, 2e

  36. Formatting Disks (cont’d.) Table 9-2, Formatting disks Connecting with Computer Science, 2e

  37. Creating Folders (Subdirectories) • Store files on disk • Done after disk partitioned and formatted • Divides disk further into folders or directories • Can also contain subfolders or subdirectories • Root: main level • Create one or more folders at root • Folder may lie within root folder • Always a current subdirectory (folder) in use • View prompt in command-line interfaces • View status bar in Windows Connecting with Computer Science, 2e

  38. Creating Folders (Subdirectories) (cont’d.) • Parent-child structure has nearly unlimited depth • Avoid creating more than 10 levels in the structure • Each OS enables user to create directories (folders) • Folders named according to specific rules • General rules • Folder names must start with a letter • Maximum length of 255 characters • UNIX: case sensitive • DOS and Windows: not case sensitive Connecting with Computer Science, 2e

  39. Creating Folders (Subdirectories) (cont’d.) Table 9-3, Creating folders Connecting with Computer Science, 2e

  40. Listing the Contents of Drives and Folders Table 9-4, Listing the contents of drives and folders Connecting with Computer Science, 2e

  41. Listing the Contents of Drives and Folders (cont’d.) Table 9-4, Listing the contents of drives and folders (cont’d.) Connecting with Computer Science, 2e

  42. Renaming Folders and Files Table 9-5, Renaming folders and files Connecting with Computer Science, 2e

  43. Deleting Folders and Files • Deleting folders requires care • Can delete all folders and files inside, too • Windows: provides recovery (Recycle Bin) • Linux: no recovery mechanism • Wildcard: symbol used to select files or directories • Asterisk (*) and question mark (?) • Examples: • c:\windows\system32\drivers\*.inf • *.exe (signifies all .exe files) • a*.bat (signifies all .bat files starting with “a”) Connecting with Computer Science, 2e

  44. Deleting Folders and Files (cont’d.) Table 9-6, Deleting folders and files Connecting with Computer Science, 2e

  45. Copying Files and Folders • Copy into folders or store at root • Possible after basic folder and file structures set up • Partitioning, formatting, and creating folders • Prepares drive to receive files • One of the most important skills to learn • Organize drives into folders • Improves work effectiveness • Helps in performing proper backups Connecting with Computer Science, 2e

  46. Copying Files and Folders (cont’d.) Table 9-7, Copying files and folders Connecting with Computer Science, 2e

  47. Moving Files and Folders • Similar to copying files • Copy command followed by delete command Table 9-8, Moving files and folders Connecting with Computer Science, 2e

  48. One Last Thought • Operating systems are a central part of computing • Learning the basic OS concepts and how to use them are essential • Concepts are taught alongside practical skills • Advanced study is recommended Connecting with Computer Science, 2e

  49. Summary • Operating systems: • Software control center of the computer • Consist of a kernel and other system programs • Loaded into RAM by program in BIOS chip • May be single tasking or multitasking • Time slicing is a method for multitasking • Basic tasks: provide user interface, manage processes, manage resources, provide security • Two interfaces: GUI and console window • Supervise program in execution (process) Connecting with Computer Science, 2e

  50. Summary (cont’d.) • Operating systems (cont’d.) • Interface hardware elements through drivers • Protect system from intended or unintended violations • OS file management: • Partitioning/Formatting disks • Creating folders (subdirectories) • Listing/Renaming folders and files • Deleting/Copying/Moving folders and files Connecting with Computer Science, 2e