CSCI-235 Micro-Computer in Science System Software

CSCI-235CSCI-235Micro-Computer in ScienceMicro-Computer in Science

System SoftwareSystem Software

© Prentice-Hall, Inc

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


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


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


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


Sharing the CPUSharing the CPU

MultiprocessingMultiprocessing MultiprogrammingMultiprogramming Time-SharingTime-Sharing


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


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


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


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


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


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


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


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


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)


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


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


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)


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


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


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


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


Graphical User Interface (GUI)Graphical User Interface (GUI)


Menu-driven User InterfaceMenu-driven User Interface


Command-Line InterfaceCommand-Line Interface


MS-DOS

WINDOWS XP MAC OS

LINUXUNIX

Popular Operating SystemsPopular Operating Systems


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)


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


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


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


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


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


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


Antivirus SoftwareAntivirus Software

Antivirus softwareAntivirus software protects the computer protects the computer from computer virusesfrom computer viruses


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


SearchSearch

Search programsSearch programs enable users to find files enable users to find files on storage deviceson storage devices


File Compression UtilityFile Compression Utility

A A file compression utilityfile compression utility reduces the size reduces the size of a fileof a file


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

Documents

CSCI-235 Micro-Computer in Science System Software