Connecting with Computer Science, 2e - Radford · PDF file · 2010-09-02– Loads and supervises all other programs ... • OS running on a computer is called a platform ... • Coordinated

Connecting with Computer Science, 2e

Chapter 9 Operating Systems

Connecting with Computer Science, 2e 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


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


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

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++



Figure 9-1, An OS provides an interface between the user, applications, and hardware

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


Figure 9-2, Users and computer components interact with the OS kernel




•  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


Table 9-1, OS development summary


Connecting with Computer Science, 2e 11 Table 9-1, OS development summary (cont’d.)



Table 9-1, OS development summary (cont’d.)


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



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


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

Functions of an Operating System (cont’d.)

•  Four main categories –  Providing a user interface –  Managing processes –  Managing resources (including memory) –  Providing security



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


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


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)



Figure 9-3, (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

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



Figure 9-4, Windows Task Manager

Managing Processes (cont’d.)


Figure 9-5, Viewing processes in Linux with the ps command




•  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



•  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


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


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


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


Using an Operating System

•  It is helpful to understand: –  How an OS works –  How to perform basic tasks

•  Skills focus: –  Basic file management tasks


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


Figure 9-6, The Windows interface for working with files and folders

Managing Disk Files (cont’d.)


Figure 9-7, Linux command-line interface for displaying files and folders

Managing Disk Files (cont’d.)


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


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 Table 9-2, Formatting disks

Formatting Disks (cont’d.)

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



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


Table 9-3, Creating folders

Creating Folders (Subdirectories) (cont’d.)


Listing the Contents of Drives and Folders

Table 9-4, Listing the contents of drives and folders


Listing the Contents of Drives and Folders (cont’d.)

Table 9-4, Listing the contents of drives and folders (cont’d.)


Renaming Folders and Files

Table 9-5, Renaming folders and files


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”)


Table 9-6, Deleting folders and files

Deleting Folders and Files (cont’d.)


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


Table 9-7, Copying files and folders

Copying Files and Folders (cont’d.)


Moving Files and Folders

•  Similar to copying files –  Copy command followed by delete command

Table 9-8, Moving files and folders


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


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)


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

Documents

Connecting with Computer Science, 2e - Radford · PDF file · 2010-09-02– Loads and supervises all other programs ... • OS running on a computer is called a platform ... • Coordinated