connecting with computer science, 2e chapter 9 operating systems

Connecting with Computer Science, 2e

Chapter 9Operating 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



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


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

connecting with computer science, 2e chapter 9 operating systems

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