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Chapter 3AChapter 3A

Operating System BasicsOperating System Basics

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Learning ObjectivesLearning Objectives3.13.1 Summarize the ways in which an operating Summarize the ways in which an operating

system works with the computer and usersystem works with the computer and user3.2 3.2 Describe the way data are moved around the Describe the way data are moved around the

computer and the basic concept of the computer and the basic concept of the machine cyclemachine cycle

3.3 3.3 List and describe the major PC operating List and describe the major PC operating systemssystems

3.4 3.4 Explain how the Windows file system Explain how the Windows file system organizes organizes its filesits files

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Types of Operating SystemsTypes of Operating Systems• Real-time operating systemReal-time operating system: A very fast, relatively small : A very fast, relatively small

OS designed to respond to requests almost instantlyOS designed to respond to requests almost instantly• Single-user/single-tasking operating systemsSingle-user/single-tasking operating systems: Allow a : Allow a

single user to perform just one task at a timesingle user to perform just one task at a time• Single-user/multitasking operating systemsSingle-user/multitasking operating systems: Allow a : Allow a

single user to perform two or more functions at oncesingle user to perform two or more functions at once• Multi-user/multitasking operating systemsMulti-user/multitasking operating systems: Allow : Allow

multiple users to use programs that are simultaneously multiple users to use programs that are simultaneously running on a single network server (a running on a single network server (a terminal serverterminal server))

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Functions of Operating SystemsFunctions of Operating Systems• Supporting programsSupporting programs• Sharing data between Sharing data between

windows and programswindows and programs• Managing the computer Managing the computer

hardwarehardware• Working with device driversWorking with device drivers

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Supporting ProgramsSupporting Programs• The operating system The operating system

manages all the other manages all the other programs that run on programs that run on the computerthe computer

• It provides services to It provides services to these programs when these programs when they use they use system calls system calls to to request the services request the services

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Windows: Sharing DataWindows: Sharing Data• ClipboardClipboard - a temporary holding place in the - a temporary holding place in the

computer’s memorycomputer’s memory– Cut command Cut command - moves the data out of the application and - moves the data out of the application and

onto the Clipboardonto the Clipboard– Copy commandCopy command - leaves the data in place and a copy of it - leaves the data in place and a copy of it

is saved on the Clipboardis saved on the Clipboard– Paste commandPaste command - moves the data from the Clipboard into - moves the data from the Clipboard into

the documentthe document• Clipboard can be used for moving data between Clipboard can be used for moving data between

different programs, a feature enhanced by different programs, a feature enhanced by OLE OLE (Object Linking and Embedding)(Object Linking and Embedding)

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Managing Computer HardwareManaging Computer Hardware• The operating system is the intermediary between The operating system is the intermediary between

the programs and the hardware devicesthe programs and the hardware devices• Processing interrupts so programs and hardware Processing interrupts so programs and hardware

subsystems work in harmonysubsystems work in harmony– An An interruptinterrupt is a request for attention by some part of a is a request for attention by some part of a

computer systemcomputer system

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Working with Device DriversWorking with Device Drivers• Device Device driversdrivers are programs that allow the OS and are programs that allow the OS and

other programs to use a hardware deviceother programs to use a hardware device• The operating system provides some of the device The operating system provides some of the device

driversdrivers• Others may come with purchase of the device Others may come with purchase of the device

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Binary and Text CodeBinary and Text Code• Binary: the computer’s number systemBinary: the computer’s number system• Text codeText code - list of- list of which combinations of bits which combinations of bits

represent which charactersrepresent which characters– ASCIIASCII : Eight-bit code that specifies characters for values from : Eight-bit code that specifies characters for values from

0 to 120 to 12– Extended ASCII Extended ASCII : : specifies characters for codes from 128 to specifies characters for codes from 128 to

255255– Unicode Worldwide Character StandardUnicode Worldwide Character Standard: : Represents each Represents each

letter, number, or symbol with up to four bytes letter, number, or symbol with up to four bytes

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Moving DataMoving Data• BusBus:: electronic path used to transfer data between electronic path used to transfer data between

hardware componentshardware components– ParallelParallel busbus: : sends information parallel across multiple sends information parallel across multiple

wireswires– Serial busSerial bus:: sends information one bit at a time in series sends information one bit at a time in series– Internal busInternal bus: Connects the CPU to memory modules: Connects the CPU to memory modules– External busExternal bus: Connects external devices to the CPU: Connects external devices to the CPU

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External Bus StandardsExternal Bus Standards• IEEE 1394IEEE 1394 : typically used to transfer video and audio : typically used to transfer video and audio

datadata• PCI busPCI bus: : designed to integrate various hardware designed to integrate various hardware

devices into a computerdevices into a computer• PCI ExpressPCI Express: : replacement technology for the PCI busreplacement technology for the PCI bus• SATASATA: : Current standard for connecting hard drives to Current standard for connecting hard drives to

the computerthe computer• USBUSB:: found on all modern personal computers and found on all modern personal computers and

supports a host of hardware devicessupports a host of hardware devices

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Cache Memory and CPUCache Memory and CPU• CacheCache - a smaller, faster memory subsystem than the - a smaller, faster memory subsystem than the

computer’s main RAMcomputer’s main RAM• The CPU has two basic parts for processing data:The CPU has two basic parts for processing data:

– ControlControl unitunit: : directs the flow of data through the CPU directs the flow of data through the CPU (Contains the CPU’s (Contains the CPU’s instruction set instruction set and is expressed in and is expressed in microcodemicrocode))

– Arithmetic logic unit Arithmetic logic unit : : Carries out the processing that Carries out the processing that involves comparing numbers (involves comparing numbers (logical operationslogical operations) or ) or carrying out carrying out arithmetic operationsarithmetic operations

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Cache Memory and CPUCache Memory and CPU• Machine cycle: Machine cycle: Complete set of steps in executing an Complete set of steps in executing an

instructioninstruction– Instruction cycleInstruction cycle

• FetchingFetching: : Retrieve a command or data from memory.Retrieve a command or data from memory.• DecodingDecoding: : Break down the command into instructions that Break down the command into instructions that

correspond to those in the CPU’s instruction set.correspond to those in the CPU’s instruction set.– Execution cycleExecution cycle

• ExecutingExecuting: : Carry out the instructions in order.Carry out the instructions in order.• StoringStoring: : Store results of the instruction in memory (not always Store results of the instruction in memory (not always

necessary).necessary).

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Operating Systems ConceptsOperating Systems Concepts• Bit size: Number of bits the OS uses to represent Bit size: Number of bits the OS uses to represent

valuesvalues• Every byte of a computer's RAM has its own unique Every byte of a computer's RAM has its own unique

numeric identifier, called an numeric identifier, called an addressaddress• Backward compatibleBackward compatible : an OS designed to work with : an OS designed to work with

most or all of the programs that were created for the most or all of the programs that were created for the old versionold version

• EmulatorEmulator – a software program designed to re- – a software program designed to re-create the exact environment of the older programcreate the exact environment of the older program

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Common Operating SystemsCommon Operating Systems• WindowsWindows• Mac OS XMac OS X• Linux for Desktop PCsLinux for Desktop PCs• Others:Others:

– DOSDOS– UnixUnix– iOSiOS– AndroidAndroid– Chrome OSChrome OS

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Organizing Disk StorageOrganizing Disk Storage• FormattingFormatting : : Magnetically mapping the disks’ surface Magnetically mapping the disks’ surface

so the computer can go directly to a specific point on so the computer can go directly to a specific point on itit

• Stages of formattingStages of formatting– Forming Forming trackstracks - concentric - concentric

rings on each side of the diskrings on each side of the disk– Dividing tracks into Dividing tracks into sectorssectors - -

locations where binary data is locations where binary data is physically storedphysically stored

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Finding Data on a DiskFinding Data on a Disk• File system File system - logical method for managing the - logical method for managing the

storagestorage• When a disk is formatted, four areas are created:When a disk is formatted, four areas are created:

– Boot sectorBoot sector: : A program that runs when the computer A program that runs when the computer starts up, in a process called starts up, in a process called bootingbooting

– File allocation table (FAT)File allocation table (FAT): : Keeps track of file locationsKeeps track of file locations– Root folderRoot folder:: A folder that holds information about all the A folder that holds information about all the

other files on the diskother files on the disk– Data areaData area: : The remaining area of the diskThe remaining area of the disk

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File SystemsFile Systems• New Technology File System (NTFS) New Technology File System (NTFS) : : A newer file A newer file

system that offers better security and performancesystem that offers better security and performance• Web-Based Distributed Authoring and Versioning Web-Based Distributed Authoring and Versioning

(WebDAV) (WebDAV) : file system describes a structure for : file system describes a structure for managing access and changes to files that are stored managing access and changes to files that are stored onlineonline

• ShortcutShortcut: : An object that points to another file; not An object that points to another file; not reflected in the disk’s actual file structure reflected in the disk’s actual file structure

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Optimizing Disk PerformanceOptimizing Disk Performance• UtilitiesUtilities:: Software programs that offer new features Software programs that offer new features

for the OS or enhance themfor the OS or enhance them– Backup utilitiesBackup utilities can help you copy large groups of files can help you copy large groups of files

from your computer to another storage mediumfrom your computer to another storage medium– Anti-malwareAnti-malware examines files, memory and parts of the examines files, memory and parts of the

operating system to detect and remove operating system to detect and remove malwaremalware – FirewallFirewall utilities examine traffic coming from your utilities examine traffic coming from your

computer to the Internet, and vice versacomputer to the Internet, and vice versa– Screen saversScreen savers display a moving image or sequence of display a moving image or sequence of

pictures on the computer screen pictures on the computer screen