Operating Systems

Computer Tech Repair Chapter 2

Operating Systems

Chapter 2


What is an Operating System?• Operating System: – Software that provides a computer user with a file

system structure and with a means of communicating with the computer hardware.

– Ensures that programs running on the computer do not interfere with each other

– The core of the operating system is referred to as the kernel.• Core is enhanced by other applications• Interface style, security, specialized file system


Operating System Characteristics

• Most operating systems appear similar when judged by they screen display (interface) but they handle activities and data storage very differently.– Multitasking – 32-Bit and 64-Bit– User Interface– File system Structure


MultitaskingMultitasking: the ability of an operating system to support two or more programs running at the same time.• Programs DO NOT run at the same time• Computer switches control from program to

program– i.e. printing, e-mail, surfing the internet, or running

another application

• Some systems do not multitask very well– Tablets or smartphones


Multitasking (cont’d)Two types of Multitasking:• Preemptive multitasking: (time slicing) the

process which allows multiple programs to share control of the operating system– No program can totally take charge of computer

system– All program share RAM at the same time• If two try to use same RAM - system locks up

– Windows 95, Me, XP, Vista, NT, 2000 & OS/2 & MAC OS/X


Multitasking (cont’d)

• Cooperative Multitasking: one program dominates the operating system but will allow another program to run while it is idle.– Windows 3.X and MAC OS/9 and earlier

• Multithreading: Data and parts of programs are shared between two or more CPUs (or multiple cores of same CPU


32-bit and 64-bit• The amount of data that can be stored or processed at

once by the CPU or the maximum amount of memory the operating system can access

• 32 bit can access 4 GB RAM• 64 bit can access 8 GB or 128GB (depending on operating system)

• Upgrade from one system to another can be affect by the number of bits it was written for – 32 bit to 32 bit or 64 to 64 ok– 32 bit directly to 64 = lost all data files

back up files, upgrade, reinstall data


User Interface

Two Dominate user interfaces:• Command Line Interface (CLI): commands are

issued by typing text.• DOS was major operating system used in the

1980’s• Used today during troubleshooting– When system fails during startup – Modern systems don’t use DOS they use a DOS

emulator


DOS Screen Shot


User Interface

• Graphical User Interface (GUI): users perform functions by selecting on screen icons rather than typing text based commands.

• Much more user friendly than DOS• As Mac gained popularity Win 3.1 and NT

helped windows retain control of operating market

• GUI displays file system as folders, icons, and names


GUI Screen Shot


File System• File: a program or collection of data that form a

single unit.• Directory and Subdirectory: are groupings of

files• Root Directory: is the top of directory system• Pathname: used to identify the location of a

specific file (C:\Users\Joe\My Pictures\mom• All operating systems use this basic structure


File System (cont’d)

• File System: method of organizing files on a storage device (how the o.s. keeps track of files)

• File Table: tracks which areas on a disk are used and which are not.– FAT12– FAT16– FAT32– NTFS (windows default since XP)


Configuration Files• Configuration Files: Information about the type of

hardware and software the system has. (Legacy File – included to support older software)

• HKEY_CLASSES_ROOT: Linking and embedding information on how files are associated with each other

• HKEY_CURRENT_USERS: Info for current user of this workstation

• HKEY_LOCAL_MACHINE: Info specific to local computer• HKEY_USERS: Info for each user of this workstation• HKEY_CURRENT_CONFIG: Display and printer settings


Configuration Files (cont’d)• Configuration files are stored in a data base called the

registry.• Registry is accessed by (start-run-regedit)• Two main registry files: system.dat & user.dat• Registry is repaired through system restore utility• CHANGES TO THE REGISTRY CAN COMPLETELY

DISABLE THE OPERATING SYSTEM!!! DO NOT EXPERIMENT WITH REGISTRY SETTINGS

• Techs rarely need to access registry files directly unless part of steps outlines in Microsoft TechNet Website.


Microsoft Windows Operating System• Most widely used OS– XP, Vista, 7, and 8

• XP weak Security• Vista over protective, transparent pages, memory hog• 7 relaxed security less memory intensive features• 8 touch screen, Tiles instead of icons, no start button

• File Directory structure changes for each version (can make it hard to fine files)

• File Names – Once XXXXXXXX.XXX max. (name.file extension)– Now up to 255 characters (long file names)– | * > < ? : \ / “ not allowed (legacy software)– File extension now just to help id file type (note .exe)


Microsoft Windows Operating System

• Desktop: user interface – similar in versions XP to 7 – Windows 8 • No start default screen is the start menu

feature• Tiles (apps)• Designed for touch screen but mouse still works• Can display traditional desktop (but no start

icon)


Window 7 Desktop


Window 8 desktop


Windows 8 Alternative


Windows Features• Windows Aero: (Vista) Various degrees of transparency

on open pages (slow, Lots of RAM, 3-d graphics card)

• Bitlocker Drive Encryption: renders files unreadable by people other than those who are allowed to read them– Entire volume including system files– Data encrypted even if os is not running– Can’t just move hard drive to another computer– Transparent after activated– System must have a TPM (trust platform module) or

firmware that can read USB flash drive


Windows Features (cont’d)

• Windows Media Center: a collection of media manipulation utilities that allows you to edit digital movies, photos or to record copy and create DVD.

• Windows Mobility Center: Provides a central location for accessing most commonly used features for laptops– Presentation & energy conserving configurations– Configures common network configurations– Hot Start Feature starts apps directly out off sleep or off

mode no need to wait for program to “load”



• Windows Meeting Space: designed for collaboration over a network 2 – 9 people. Users can share files, doc, photo etc. (Windows 8 uses the cloud)

• Network Discovery: automatically detects and configures a network and shares an internet connection– NOTE: Some routers are not compatible



• Windows Shadow Copy & Previous Versions: when loading new version of windows it automatically makes and saves copies of files that have been changed.– To restore open: properties/previous

versions/restore– Useful if upgrade fails or critical software is not

compatible with up grade



• Windows Ready Boost: Allows the OS to use a flash drive to temporarily store data that is too big to be held in RAM and would normally be temporarily written to the hard drive. – Speed up computer performance– Avoids crashes when RAM is full

• Windows Defender: Works with Internet Explorer 7 to protect computer from spyware. User can ignore, allow, quarantine or always allow a file



• Tablet PC Settings: Touch screen support– Can also convert hand writing to text

• Offline Files: synchronizes files that are stored on a network server with a copy on a computer. (Cloud storage does the same thing )

• XP Mode: allows you to run software written for XP– Two free downloads: 1. window virtual PC 2. XP

mode– XP is running simultaneously with Windows 7



Libraries: a virtual container of user content (My Documents, My Music, My Pictures, My Videos)Bitlocker to Go: an enhanced version of Bitlocker that allows encryption of a USB storage device

- Free download- encrypt files, remove USB, and use in another computer


Windows 8 Specific Features

Microsoft User Account: user can log on to a computer two ways:• Local User: logs onto computer only• Microsoft account: User logs onto internet, e-mail

account, Facebook, Twitter, LinkedIn and an assortment of other accounts

Windows to Go: Allows Windows 8 and desired files and folders to run from a USB• Allows techs boot any computer to their own

personal computer configuration


Windows 8 Specific Features (cont’d)

• Sync Your Settings: When you log onto you Microsoft account from any device that automatically connects to the cloud the device will match your personal settings.

• Picture Password: logon using a PIN or selecting a picture and creating a combination of circles, taps, and lines.

• Recovery Refresh and Reset: automatically repair OS– Refresh reinstalls Windows 8 and retains personal files & apps – Reset OS ,all personal files and apps are lost. Only OS and

standard apps are reinstalled.– Located in: Advances tools\Recovery


Windows Installation

• Upgrade: retains files, settings and applications• Clean install: (custom install) Previous OS is

completely replaces all files, settings, applications will be lost.– XP to 7 requires custom install– Some software, drivers or hardware may not be

supported in newer versions of windows– Run the Windows upgrade advisor– Run clean install after partitioning or reformatting hard

drive then reinstall personal files from backup (avoids registry corruption)


Windows Installation (cont’d)

• Always backup entire computer system before performing any upgrade!

• Check System Requirements– Each version of windows has its own set of requirements– Each edition of each version of windows has it own

requirements• Windows Easy Transfer (Windows 7) allows transfer

of user accounts, files and settings to a USB drive (similar to backup)then after custom install use tool to reinstall files and settings


Windows Installation (cont’d)

• Windows Anytime Upgrade: user can download features as needed only works until newer OS is available.

• Windows PE: a minimal 32 bit OS that prepares disk storage system before complete OS is installed.– Can be used to recover a failed computer system

for troubleshooting– Part of WAIK ( Windows Automated Installation

Kit) Free down load from support website


Windows Boot Sequence

• Boot Sequence: is the step by step process of bringing a computer to operational status.

• Cold Boot (hard boot): Power is off and turned on

• Warm Boot (soft boot):restarting a computer that is already running) [Ctrl],[Alt], and [Delete] keys or clicking Restart


Windows Boot Sequence (cont’d)

• POST (Power On Self Test)– One Beep all is well– Series of beeps and error code• Check manufactures website for error code list

• BIOS based system – short bootstrap program runs the post and searches for the first sector of the hard drive called MBR(master boot record), loads basic file into RAM and turns computer over to OS



• UEFI (Unified Extensible Firmware Interface) based system:– POST is completed– Control is turned over to boot manager program

instead of MBR– Avoids unauthorized changes to operating system– Protects computer before OS is started– Often still called BIOS



• Boot manger displays boot menu• Boot manager loads ntoskrnl.exe and hal.dll

into memory and scan registry for device driver to load. Then passes control over to the kernel

• Kernel loads drivers and hal.dll and initializes computer setting with values stored in the system registry.



• The Kernel starts the session manager (smss.exe) which creates the environment

• OS switched to graphic mode and loads winlogon.exe thus starting the logon manager

• Logon manager waits for user input.• User types id and password• Logon manager checks user registry• And away you go…


Windows Boot Sequence (cont’d)• Dual Boot System: Two operating systems are

installed on a single computer.• Multiple boot System; more that two Os are installed

on a single machine Linux, Window 7 and Vista– Can only run one OS at a time – Window 8 is not possible with dual/multi boot (use virtual

machine)• Virtual Machine: (virtual PC) Can run both OS at

same time using special application– Windows Virtual PC or VMware


• Mobile Device Operating System: Designed for devices with limited hardware resources– Apple, android etc.

• Cloud Computing: Sharing a pool of resources over the internet– Storage, Application software, Instant messaging– Unlike computers mobile devices only load a small

portion of application software (app) the rest of the software is on a cloud service

– The mobile device is referred to a thin client– Software provided through the cloud is referred to

as a virtualization


Common operating System Terms

• Application software (end-user software): Software designed for a specific purpose. It is not an OS. i.e. Word, Excel, PowerPoint

• Software driver: small software package that allows communication between the computer and peripheral device.– Incorrect drivers can cause problems• i.e. install a new printer, self test run perfectly, but

printer prints garbled text or endless blank pages


Common operating System Terms

• Software Patch: A fix for a bug in an OS or Application software that has already been released

• Service Pack: a large collection of patches released at one time.

• End of Chapter 2!

Operating Systems

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