software slide show

7/27/2019 Software Slide Show

1/35

System Software

Types


2/35

Types of System Software

Operating SystemDevice Drivers Software that acts as'translator' between programs and hardware

devicesPlug and playHot plugging


3/35

Types of System Software (cont)

Utilities programs to keep PC runningefficiently

Some included with OS e.g Scandisk, DiskDefragmenter, BackupThird party utility software, e.g. Norton Utilities,

Anti-virus packages, WinZip, etc.Programming languages, Assemblers,

Interpreters, CompilersDBMS (Database Management System), e.g.Oracle SQL Server, MySQL, DB2


4/35

Malicious programs

Viruses:Boot sector virus

Executable virus

Macro virus

Worms A program that copies itself into memory, disks or through network connections disk space/memory canbecome full

Trojan horseDisguised as something useful when opened candamage PC or provide 'back-doors'


5/35

System Software

Structure of an Operating System


6/35

Main Components of OperatingSystems

The user interface the part of the OS thathandles the dialogue with the user. GUI(graphic user interface) or WIMP (Windows,icons, mouse and pointers).The Kernel (Nucleus) The central moduleof the operating system that is loaded intomemory when the computer starts up andremains there until the computer switches off.


7/35

The Kernel

It is responsible for Memory ManagementProcess Management

Storage ManagementThe aim of the kernel is to:

Minimize turnaround time

Maximize throughput.Utilize resources as efficiently as possible .


8/35

Process Management

A process is a program or task that iscurrently being executed .Kernel must ensure each process receives

the resources it requires.Ensures that processes follow sequence in alogical order by using a scheduler.Handles processes in multitasking so that

they appear to be running simultaneously.


9/35

Memory Management

The OSAssigns each program the memory it requiresMonitors the contents of the memory

Clears items out of memory when they are nolonger needed.Handles illegal access to memory blocks(called exceptions)


10/35

Memory Areas

RAM Main system memoryVirtual Memory Using an area of the Hard Drive as if it wereRAM. Also called a swap file.

Thrashing is when the computer uses too much Virtualmemory and there is not enough RAM .

Buffers are small storage areas in RAM for device I/O. They aresmall and fast. Eg. Mouse, keyboard.SPOOLers (Simultaneous Peripheral Operation On Line) arelarger storage areas on the hard disk for device I/O. They arelarge and slow. Eg. Printer.


11/35

Processing Techniques

Software Component


12/35

Single-tasking

Only one program can be processed at atime.Resources are all allocated to the single

program that is being used.Only one user at a time.


13/35


14/35

Multi-tasking 2

Co-operative multi-tasking Each program can control the CPU for as long asit needs.

Eg. Windows 3.1Pre-emptive multi-tasking

The OS controls the use of the CPU

Order is maintained and monitored.Eg. Windows 95 onwards, OS/2 and UNIX.


15/35

Multi-threading

Program is designed to work in pieces calledthreads. OS can execute different threads

simultaneously.Threads must be designed by theprogrammer .

E.g. Spell checker in Word checks spellingwhile you type.


16/35

Multi-processing

Can only be achieved if there is physically more thanone processor in the computer .Each processor is capable of executing a differentprogram or part of program.

Threads also work well with multi-processingsystems.Requires a special MotherboardRequires an OS that supports multi-processing.

Multi-processing supports up to 128 Processors .More than 128 Processors must by placed in aseparate system this is then called parallelprocessing.


17/35

Batch Processing

Jobs and their associated data are collectedin a single batch at a central location andthen they are processed without user

intervention .Eg. A Bank stores all of the loan transactionsdone for that day on a server and then thetransactions are only processed that nightafter the bank is closed. Common use todayis Payroll.


18/35

Real-time processing.

Software that controls the processing keepstrack of an external process and keepsupdating.

Eg. ATM Banking as you are drawingmoney the ATM is updating your account atthe main bank branch. You see your balanceimmediately.

Other examples space shuttle, power plants, bookings over the internet, on-lineshopping.


19/35

Which Operating Systems?

Single-taskingMS-DOS, Palm OS

Multi-taskingMulti Tasking, Windows 95/98/2000/XP/VistaUnix, Mac OS X, Linux

Multi-processing

Windows NT/2000/XP/VistaUnix, Mac OS X, Linux


20/35

System Software

BIOS, CMOS, REGISTRY


21/35

BIOS Basic Input Output System

Built-in software used to control hardwareat lowest possible levelStored on ROM chips

Boots PC and manages flow of data betweenOS and certain attached devicesSettings configurable, e.g. clock speed, order

in which PC boots, etc.Software 'talks' to BIOS by means of softwareinterrupts


22/35

CMOS Complimentary Metal OxideSemi-conductor

Type of memory chip non-volatile batteryStores 2 types of data

Data read by BIOS during start-up (info about

CPU, RAM type, keyboard, drives, etc.Data set by user (date, time, boot sequence,etc.)


23/35

Registry

In Windows OS:Hierarchical database info about

System

SoftwareDriversPeripheralsUsers


24/35

Fragmentation

When files aredeleted from andwritten to HD parts

of same file getscattered across HDIn diagram:

Red: MyDoc.docGreen: Salaries.xlsYellow: Database

All files fragmented

Fragmented files


25/35

Fragmentation

Result: Slows downopening of any of these files

Fragmented files


26/35

Fragmentation

Disk Defragmenter rewrites files so thatall parts of file in one

contiguous space onHDIn diagram:

Red: MyDoc.docGreen: Salaries.xlsYellow: Database

All files nowdefragmented

Defragmented files


27/35

Fragmentation

Defragmentationdoes NOT createmore space on HD

only speeds upreading of the files

Defragmented files


28/35

DLL files

A Dynamic Link Library (DLL) is a file of codecontaining functions that can be called fromother executable code (either an applicationor another DLL).Programmers use DLLs to provide code thatthey can reuse to do specific jobs.

Unlike an executable (EXE) file, a DLLcannot be directly run. DLLs must be calledfrom other code that is already executing.


29/35

Open source versus other software


30/35

Windows versus Linux

Windows Linux

Created by theMicrosoft company.

Originally created by LinusTorvalds who freely distributedthe source code has sincebeen modified and adapted byseveral people.

Licensing fees are paidto install and run it on acomputer.

No licensing costs are paid.


31/35

Important Terms

Intellectual Property Product of someone's thoughts. Copyright isapplicable.

Software Licenses The right to load a program on your computer.Distribution

Distribution package of Linux e.g. SuSE,Debian, Red Hat.


32/35

Open source software

License given to access and modify sourcecode. The modified code may not be sold must be distributed freely.

Called a GPL ( General P ublic License).


33/35

Advantages of Open source software

No cost / low cost (usually free). Access to source code.Freedom to adapt and change the software tosuit your own needs.

Access to a community of users / support.


34/35

Disadvantages of Open source software

No one to hold responsible.Risk of poor support.

Higher skills needed if you want to use thismodel to its fullest potential.Various varieties of the same software can

arise.


35/35

Proprietary software Shrinkwrap Shareware Freeware

What you buy instores, softwarein boxes sealedwith shrink wrap.

Download. Uses the Try before you buy concept if you like the software and want to useit past the trial date / access all thefeatures you must pay a license fee.

Usually cheaper than shrink wrappedsoftware because you do not have topay a middle man .

Download. Free.

May not becopied. May only be usedon one computer.

Copy / share with your friends. Copy / share with your friends.

Usually limited in features / time. Differs from open source softwarebecause the software is free butyou cannot access the source code.

software slide show

Documents