Transcript Connecting with Computer Science, 2e

Connecting with Computer
Science, 2e
Chapter 9
Operating Systems
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
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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
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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
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What Is an Operating System?
• Program responsible for managing the user
interface, system resources, and processes
• Software control center
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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++
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What Is an Operating System? (cont’d.)
Figure 9-1, An OS provides an interface between the user,
applications, and hardware
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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
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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
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What Is an Operating System? (cont’d.)
Figure 9-2, Users and computer components interact with
the OS kernel
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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
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What Is an Operating System? (cont’d.)
Table 9-1, OS development summary
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What Is an Operating System? (cont’d.)
Table 9-1, OS development summary (cont’d.)
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What Is an Operating System? (cont’d.)
Table 9-1, OS development summary (cont’d.)
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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
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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
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Functions of an Operating System
• Basic functions
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Provide a user interface
Schedule and manage program execution
Manage memory
Configure devices
Provide file management and security
Provide basic networking capability
Monitor performance
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Functions of an Operating System
(cont’d.)
• Four main categories
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Providing a user interface
Managing processes
Managing resources (including memory)
Providing security
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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
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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
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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)
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Providing a User Interface (cont’d.)
Figure 9-3, (cont’d.)
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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
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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
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Managing Processes (cont’d.)
Figure 9-4, Windows Task Manager
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Managing Processes (cont’d.)
Figure 9-5, Viewing processes in Linux with the ps command
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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
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Managing Processes (cont’d.)
• Time slicing
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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
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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
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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
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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
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Using an Operating System
• It is helpful to understand:
– How an OS works
– How to perform basic tasks
• Skills focus:
– Basic file management tasks
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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
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Managing Disk Files (cont’d.)
Figure 9-6, The Windows interface for working with
files and folders
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Managing Disk Files (cont’d.)
Figure 9-7, Linux command-line interface for displaying files and folders
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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
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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
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Formatting Disks (cont’d.)
Table 9-2, Formatting disks
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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
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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
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Folder names must start with a letter
Maximum length of 255 characters
UNIX: case sensitive
DOS and Windows: not case sensitive
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Creating Folders (Subdirectories)
(cont’d.)
Table 9-3, Creating folders
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Listing the Contents of Drives and
Folders
Table 9-4, Listing the contents of drives and folders
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Listing the Contents of Drives and
Folders (cont’d.)
Table 9-4, Listing the contents of drives and folders (cont’d.)
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Renaming Folders and Files
Table 9-5, Renaming folders and files
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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”)
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Deleting Folders and Files (cont’d.)
Table 9-6, Deleting folders and files
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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
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Copying Files and Folders (cont’d.)
Table 9-7, Copying files and folders
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Moving Files and Folders
• Similar to copying files
– Copy command followed by delete command
Table 9-8, Moving files and folders
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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
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Summary
• Operating systems:
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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)
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Summary (cont’d.)
• Operating systems (cont’d.)
– Interface hardware elements through drivers
– Protect system from intended or unintended violations
• OS file management:
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Partitioning/Formatting disks
Creating folders (subdirectories)
Listing/Renaming folders and files
Deleting/Copying/Moving folders and files
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