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 2

3. Objectives –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 3

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 4

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 5

6. 6 Figure 9-1, An OS provides an interface between the user, applications, and hardware What Is an Operating System?

7. Parts: –Kernel: core program loaded at boot time by BIOS Small to larger 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 7

8. 8 Figure 9-2, Users and computer components interact with the OS kernel What Is an Operating System?

9. Microsoft Windows –Most widely used OS on PC’s Disk Operating System ( DOS ) as a predecessor to Windows Macintosh is used in schools Linux or UNIX is used on many servers 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 9

10. 10 Table 9-1, OS development summary What Is an Operating System?

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

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

13. Types of Operating Systems Classified by features or intended uses –Single-tasking: DOS and early Mac 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 13

14. Types of Operating Systems 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 14

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 15

16. Functions of an Operating System The functions mentioned on the previous slide are divided into four main categories –Providing a user interface –Managing processes –Managing resources (including memory) –Providing security Connecting with Computer Science, 2e 16

17. Providing a User Interface User interface –Program enabling communication between the user and the Operating System –Several types, but basically two general Command line interface Graphical user interface ( GUI ) Connecting with Computer Science, 2e 17

18. Providing a User Interface DOS and Linux use a command-line interface –Sometimes called console operating systems –Normally, a single color screen where you 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

19. Providing a User Interface 19 Figure 9.3 DOS Screen

20. Providing a User Interface Graphical user interface ( GUI ) –Information displayed in a graphical format User can select items using a pointing device such as a mouse) –Clicking icons and buttons opens graphical windows and allows menu selections Connecting with Computer Science, 2e 20

21. Providing a User Interface 21 Figure 9.3a Windows 8.1 Screen

22. Providing a User Interface Windows ( Vista, 7, 8.x ) 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

23. 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 DOS currently has no command to list processes Connecting with Computer Science, 2e 23

24. Connecting with Computer Science, 2e 24 Figure 9-4, Windows Task Manager Managing Processes

25. Linux displays information on active processes –Use the ps command Connecting with Computer Science, 2e 25

26. Managing Processes A CPU can 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 can run 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

27. Managing Processes 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

28. 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

29. 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

30. 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

31. 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

32. 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 ( using Explorer ) Manages files through graphical interface Connecting with Computer Science, 2e 32

33. Connecting with Computer Science, 2e 33 Figure 9-6, The Windows interface for working with files and folders Managing Disk Files

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 34

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 35

36. Connecting with Computer Science, 2e 36 Table 9-2, Formatting disks Formatting Disks

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 37

38. Creating Folders (Subdirectories) 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 38

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

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

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

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

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 43

44. Connecting with Computer Science, 2e 44 Table 9-6, Deleting folders and files Deleting Folders and Files

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 45

46. Connecting with Computer Science, 2e 46 Table 9-7, Copying files and folders Copying Files and Folders

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

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 48

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 49

50. Summary Operating systems –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 50

51. The End 51