System Software

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System Software

• Grade 11 Chapter 2
• Pg 33

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System Software

• A set of programs that enable everything in your
  computer to work together
• Makes it possible for applications software to
  work on any computer irrespective of hardware
  configuration
• Must be able to support a wide variety of
  application programs

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Multiple software layers

• This is the key to versatility
• System software includes
• BIOS
• Drivers
• Operating system
• Utilities
• Anti-virus software
• Compilers
• Communication software

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Multiple software layers

• The levels are
• Application software
• System software
• Operating system
• Drivers / BIOS
• Hardware

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BIOS

• Typically placed on a ROM chip
• BIOS contains
• Diagnostic routines
• The initializing routine
• The Bootstrap loader

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CMOS

• Type of memory chip that retains its data when
  power is turned off as long as it receives a
  trickle of electricity from a battery.

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CMOS

• Two types of data is stored
• Data read during the diagnostic routine (such as
  info about CPU,RAM type, chipset etc)
• Data set by the user such as date, time, boot
  sequence, how fast your computer reads from
  memory,whether or not your cache is enabled or
  disabled.

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Drivers

• Allow the operating system to access and control
  hardware not supported by the BIOS

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Drivers

• Every device must have a driver
• Many drivers such as keyboard drivers come with
  the operating system
• Other drives are loaded when the device is
  connected to the computer

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Drivers

• In DOS systems drivers are files with a SYS
  extension
• In Windows environment drivers have a DRV
  extension
• A driver acts as a translator between the device
  and programs that use the device
• Each device has its own set of commands that only
  its driver knows

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Configuring a system

• Is the way in which the hardware and software of
  a computer is planned and set out.

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Configuring the environment

• This is setting up and configuring the computer
  so that it looks like home
• The backgrounds
• The screen saver
• The startup sounds
• Starting programs automatically
• The font that is displayed
• The number of colours
• The screen resolution
• The way files are shown

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Assigning resources

• Linking and communicating with memory
• IRQs
• I/O Range

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What is an IRQ

• It enables a peripheral or hardware device to
  interrupt whatever the computer is doing so that
  it can communicate with the CPU

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What is the I/O Range

• A range in memory that the peripheral can use to
  transfer data

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Configuring a computer

• Means making sure that these resources (IRQs and
  I/O Ranges) are unique for each device and that
  there are no conflicts so that all the devices /
  peripherals installed all work together in
  harmony.

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Plug and Play

• Plug and Play means that a user should be able
  to
• Insert and remove devices at will
• Connect to and disconnect from a network at will
  by simply attaching/removing a cable.

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General housekeeping

• Machines need attention and servicing this is
  called housekeeping

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Managing your computer system

• CHKDSK
• Allows you to see basic info / problem on the
  hard drive (DOS)
• Diskcopy
• Allows you to copy an entire disk (DOS)
• Format
• Cleans a disk getting it ready to be used

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Managing your computer system

• Recycle Bin
• Allows you to retrieve accidentally deleted files
• The term utility refers to software that solves
  narrowly focused problems or those related to
  computer system management.

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Utility programs

• Uninstall utility
• Uninstall a program properly
• Crash guard utility
• To catch program crashes and allow you to save
  your data
• Utilities that change and improve the way Windows
  Explorer works
• File Compression Utility
• This shrinks the size of the file so tht it takes
  up less space e.g WinZip

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Looking after data

• Disks are divided into tracks and sectors
• A number of sectors together form a cluster
• A cluster is the minimum addressable unit on your
  hard drive
• When data is written to a hard drive, it is
  written to a group of sectors, i.e cluster

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Looking after data

• The address of clusters are stored in the File
  Allocation Table (FAT)
• Operating system uses FAT to gain access to
  appropriate areas of the hard disk

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What is fragmentation

• Files that are not stored in contiguous order
  are said to be fragmented
• A lost cluster is one that is not actually used
  by ant file
• File is not marked as unused in the FAT
• Cross-linked files when two files appear to be
  claiming the same space
• Lost cluster and Cross-linked are often referred
  to as Widows and Orphans

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Using Scandisk

• Scandisk picks up lost clusters and allows the
  user the option of deleting them or turning them
  into files in order to let you examine them

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Defragmenting

• Looks at your drive and tells you what percentage
  of the hard drive is fragmented
• Rearranges files, storing each file in a
  continuous block of sectors

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Backing up

• A means of copying large amounts of information
  onto secondary storage
• Stiffy
• Disk
• Tape drive

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Viruses

• A computer virus is a program which was created
  deliberately in order to copy itself (without the
  users intention, consent or knowledge) and then
  do things that are unexpected and unwanted.

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Viruses

• Boot sector viruses
• Infects the boot sector of the disk
• Executable virus
• This attaches itself to the end of an .exe or
  .com file. It changes the startup instruction of
  the program and loaded into memory.
• Macro virus
• Program specific activated within programs that
  run macros.

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What is a worm?

• Program that copies itself into memory, a disk or
  through network connections, and alters data on
  the way
• Worms sometimes terminate after launching a copy
  somewhere else and are then referred to as
  rabbits.

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Other housekeeping tips

• Organize your hard drive
• Ensure that your hard drive is properly
  organized.
• Empty the recycle bin
• Start up disk
• It is important to have an up-to-date boot disk,
  and copies of your drive

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Other housekeeping tips

• Password / User names
• Store these on paper in a safe place
• Program Serial Number
• Paste a copy of each programs serial number to
  its case
• remove temporary files
• Windows creates many temporary files that quickly
  take up unnecessary space
• Uninstalling
• Used to remove application no longer required
  including registry entry