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CSCI-235CSCI-235Micro-Computer in ScienceMicro-Computer in Science
System SoftwareSystem Software
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System SoftwareSystem Software
System softwareSystem software includes all of the programs includes all of the programs needed to keep a computer and its peripheral needed to keep a computer and its peripheral devices running smoothlydevices running smoothly
Two major categories of system software are:Two major categories of system software are: Operating systems Operating systems System utilitiesSystem utilities
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The Operating SystemThe Operating System
The The operating system (OS) is a set of programs (OS) is a set of programs that perform certain basic functions with a that perform certain basic functions with a specific type of hardwarespecific type of hardware
The functions of the OS are:The functions of the OS are: Starting the computerStarting the computer Managing programsManaging programs Managing memoryManaging memory Handling messages from input and output devicesHandling messages from input and output devices Enabling user interaction with the computerEnabling user interaction with the computer
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The Operating SystemThe Operating System
OS stays behind the scenesOS stays behind the scenes All software depends on the OSAll software depends on the OS
OperatingOperatingSystemSystem
GUI
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Operating Systems for Large Operating Systems for Large ComputersComputers
Resource allocationResource allocation Assigning computer resources to certain Assigning computer resources to certain
programs and processes for their useprograms and processes for their use
Main issues related to resource allocationMain issues related to resource allocation Sharing the Central Processing Unit (CPU)Sharing the Central Processing Unit (CPU) Sharing memorySharing memory Sharing storage resourcesSharing storage resources Sharing printing resourcesSharing printing resources
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Sharing the CPUSharing the CPU
MultiprocessingMultiprocessing MultiprogrammingMultiprogramming Time-SharingTime-Sharing
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MultiprocessingMultiprocessing
The use of a powerful computer with The use of a powerful computer with multiple CPUsmultiple CPUs
Multiple programs run simultaneouslyMultiple programs run simultaneously Each runs on its own processorEach runs on its own processor
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MultiprogrammingMultiprogramming
Two or more programs executed Two or more programs executed concurrentlyconcurrently Programs take turns using the CPUPrograms take turns using the CPU Event-drivenEvent-driven
• AnAn interrupt interrupt suspends processing to allow another suspends processing to allow another program to runprogram to run
• After the second program runs, the OS returns the After the second program runs, the OS returns the CPU to another programCPU to another program
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Time-SharingTime-Sharing
Programs take turns using the CPUPrograms take turns using the CPU Time-drivenTime-driven
Each user is given a slice of time (fraction of a second)Each user is given a slice of time (fraction of a second) CPU works only on that user’s tasks during his/her time CPU works only on that user’s tasks during his/her time
sliceslice
Typically used in applications with many usersTypically used in applications with many users
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Starting the ComputerStarting the Computer
BootingBooting – The process of loading or – The process of loading or reloading the OS into the computer’s reloading the OS into the computer’s memorymemory
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Starting the ComputerStarting the Computer
The computer copies the The computer copies the kernelkernel from the from the hard drive into the computer’s memoryhard drive into the computer’s memory The kernelThe kernel
• Is the central part of the OSIs the central part of the OS• Starts all applicationsStarts all applications• Manages devices and memoryManages devices and memory• Resides in memory at all timesResides in memory at all times• Performs other essential functionsPerforms other essential functions
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Managing ProgramsManaging Programs Single-taskingSingle-tasking systems run one application systems run one application
program at a timeprogram at a time
MultitaskingMultitasking OSs have the ability to run more OSs have the ability to run more than one application program at a timethan one application program at a time
Multitasking is accomplished byMultitasking is accomplished by
A A foregroundforeground application application
• The active program or program in useThe active program or program in use
One or more One or more backgroundbackground applications applications
• Inactive program(s) or program(s) not in useInactive program(s) or program(s) not in use
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Example of MultitaskingExample of Multitasking
Background Background applicationapplication
Foreground Foreground applicationapplication
Storage StructureStorage Structure Programs must be in main memory (RAM) to executePrograms must be in main memory (RAM) to execute Von-NeumannVon-Neumann architecture architecture
Load instruction from memory into Load instruction from memory into instruction registerinstruction register Operands fetched from memory to internal registersOperands fetched from memory to internal registers
START
Fetch next instruction fromMemory to IR
Increment PC
Decode and ExecuteInstruction in IR
STOP ?NO YES
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Storage StructureStorage Structure Ideally, we want programs and data to reside in main Ideally, we want programs and data to reside in main
memory permanentlymemory permanently Main memory is usually too smallMain memory is usually too small Main memory is Main memory is volatilevolatile – loses contents on power loss – loses contents on power loss
Secondary storageSecondary storage holds large quantities of data, holds large quantities of data, permanentlypermanently Magnetic disk is the most common secondary-storage Magnetic disk is the most common secondary-storage
devicedevice
Actually, a Actually, a hierarchy of storagehierarchy of storage varying by varying by speedspeed, , costcost, , sizesize and and volatilityvolatility
Storage-Device HierarchyStorage-Device Hierarchy
Storage TechnologyStorage Technology
Static RAM (SRAM)Static RAM (SRAM) 0.5ns – 2.5ns, $2000 – $5000 per GB0.5ns – 2.5ns, $2000 – $5000 per GB
Dynamic RAM (DRAM)Dynamic RAM (DRAM) 50ns – 70ns, $20 – $75 per GB50ns – 70ns, $20 – $75 per GB
Magnetic diskMagnetic disk 5ms – 20ms, $0.20 – $2 per GB5ms – 20ms, $0.20 – $2 per GB
Ideal memoryIdeal memory Access time of SRAMAccess time of SRAM Capacity and cost/GB of diskCapacity and cost/GB of disk
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Managing MemoryManaging Memory
The operating system allocates memory The operating system allocates memory areas for each running program; it keeps areas for each running program; it keeps programs from interfering with each otherprograms from interfering with each other
The operating system uses The operating system uses virtual memoryvirtual memory as an extension of random access as an extension of random access memory (RAM)memory (RAM)
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ManagingManaging Virtual MemoryVirtual Memory
least recentlyused data or
program instructions
pageswapped
out
swap file
Virtual memorymanagement
hard diskpage
swapped in
most recentlytransferred data or
program instructions
memory
Virtual Memory and CacheVirtual Memory and Cache
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Cache/VM: AnalogyCache/VM: Analogy You are going to do some research on a particular You are going to do some research on a particular
topic. Thus, you go to the library and look for the a topic. Thus, you go to the library and look for the a shelve that contains books on that particular topicshelve that contains books on that particular topic
You pick up a book from the shelve, find a chair, seat You pick up a book from the shelve, find a chair, seat and start readingand start reading
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Cache/VM: AnalogyCache/VM: Analogy You find a reference to another book on the same topic You find a reference to another book on the same topic
that you are also interested in reading. Thus, you stand that you are also interested in reading. Thus, you stand up, go to the same shelve, leave the first book and pick up, go to the same shelve, leave the first book and pick up the other bookup the other book
Then, you go back to the chair and start reading the Then, you go back to the chair and start reading the second booksecond book
Later on you realize that you want to read the first book Later on you realize that you want to read the first book once again (or another related book). Thus, you repeat once again (or another related book). Thus, you repeat the same process (i.e., go to the shelve to find it)the same process (i.e., go to the shelve to find it)
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Cache/VM: AnalogyCache/VM: Analogy Suppose that instead of taking just one book from the shelve, Suppose that instead of taking just one book from the shelve,
you take 10 books on the same topic. Then, you find a table you take 10 books on the same topic. Then, you find a table with a chair, put the 10 books on the table, sit there and start with a chair, put the 10 books on the table, sit there and start reading one of the booksreading one of the books
If you need another related book, there is a good chance that it If you need another related book, there is a good chance that it is on your table so you don’t have to go to the shelve to get it. is on your table so you don’t have to go to the shelve to get it. Also, you can leave the first book on the table and there is a Also, you can leave the first book on the table and there is a good chance that you will be needing it again latergood chance that you will be needing it again later
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Handling Input and OutputHandling Input and Output Input and output devices generate Input and output devices generate
interruptsinterrupts, or signals, that tell the operating , or signals, that tell the operating system that something has happenedsystem that something has happened
The OS provides The OS provides interrupt handlersinterrupt handlers or mini- or mini-programs that begin when an interrupt programs that begin when an interrupt occursoccurs
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Providing the User InterfaceProviding the User Interface
The The user interfaceuser interface is that part of the OS is that part of the OS with which the user interacts with a with which the user interacts with a computercomputer
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Types of User InterfacesTypes of User Interfaces Graphical user interface (GUI)Graphical user interface (GUI)
Uses graphics to create a desktop environmentUses graphics to create a desktop environment Icons (small pictures) represent computer resourcesIcons (small pictures) represent computer resources Programs run within on-screen windowsPrograms run within on-screen windows
Menu-drivenMenu-driven Text-based menus are used to show all of the Text-based menus are used to show all of the
options available to the useroptions available to the user
Command-lineCommand-line The user is required to type keywords or commands The user is required to type keywords or commands
in order to enter data or give instructionsin order to enter data or give instructions
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Graphical User Interface (GUI)Graphical User Interface (GUI)
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Menu-driven User InterfaceMenu-driven User Interface
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Command-Line InterfaceCommand-Line Interface
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MS-DOS
WINDOWS XP MAC OS
LINUXUNIX
Popular Operating SystemsPopular Operating Systems
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Microsoft WindowsMicrosoft WindowsClick to view each Windows version (1985-2001)Click to view each Windows version (1985-2001)
Windows 1.0 (1985)Windows 2.0 (1987)Windows 3.x (1990-1992)Windows NT (1993)Windows 95 (1995)Windows 98 (1998)Windows 2000 (2000)Windows ME (2000)Windows XP (2001)
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MAC OSMAC OS Created in 1984 Created in 1984
First OS to use First OS to use graphical user graphical user interfaceinterface
Easiest operating Easiest operating system for system for beginnersbeginners
Mac OS X, was Mac OS X, was released in 2000released in 2000
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MS-DOSMS-DOS
Developed for IBM PCs in Developed for IBM PCs in 19811981
Uses command-line Uses command-line interfaceinterface
Use is diminishingUse is diminishing
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UNIXUNIX
Developed by AT&T Developed by AT&T in 1970sin 1970s
Developed concepts Developed concepts of file management of file management and path namesand path names
Widely used by Widely used by corporationscorporations
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LinuxLinux Developed in Developed in 1991 by UNIX1991 by UNIX
Open-source Open-source codecode – –Available Available for all to see and for all to see and useuse
More stable than More stable than WindowsWindows
Powerful and freePowerful and free
Growing Growing acceptanceacceptance
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System Utilities: Tools for System Utilities: Tools for HousekeepingHousekeeping
System utilities are programs that help the System utilities are programs that help the operating system manage the computer operating system manage the computer system’s resourcessystem’s resources
Types of utilitiesTypes of utilitiesBackup softwareBackup softwareAntivirus softwareAntivirus softwareDisk scanning Disk scanning Disk defragmentation Disk defragmentation File managementFile managementFile-searching softwareFile-searching softwareFile compressionFile compression
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Backup SoftwareBackup Software
Backup softwareBackup software includes programs that includes programs that enable the user to copy data from the hard enable the user to copy data from the hard disk to another storage mediumdisk to another storage medium
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Antivirus SoftwareAntivirus Software
Antivirus softwareAntivirus software protects the computer protects the computer from computer virusesfrom computer viruses
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File Management UtilitiesFile Management Utilities Known as a Known as a file managerfile manager Enables the user to perform Enables the user to perform
various tasks on storage various tasks on storage devices using files, folders, devices using files, folders, and directoriesand directories
Tasks include:Tasks include: Creating foldersCreating folders Saving, deleting, copying, Saving, deleting, copying,
and moving files and foldersand moving files and folders Examining the contents of Examining the contents of
filesfiles Launching application Launching application
programsprograms
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SearchSearch
Search programsSearch programs enable users to find files enable users to find files on storage deviceson storage devices
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File Compression UtilityFile Compression Utility
A A file compression utilityfile compression utility reduces the size reduces the size of a fileof a file
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TroubleshootingTroubleshooting Computer startup failureComputer startup failure
Use a boot disk (emergency disk) in the Use a boot disk (emergency disk) in the floppy drivefloppy drive
System slowdownSystem slowdown Scan for virusesScan for viruses Defragment the hard diskDefragment the hard disk
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