Computer Software

Mr Arthur

Aims of Lesson 1

1. Go over Network test

2. What is an Operating System?

3. Bootstrap Loader

4. Single user OS

5. Functions of single user OS

Operating System

The OS is a program that controls the entire operation of the computer and any peripherals connected

Key functions Interpreting user commands Displaying data on screen Saving files to backing storage Provides security Controls input/output

Bootstrap Loader

The Bootstrap loader is a small part of the OS stored on ROM

Its function is to load the rest of the OS from the hard disk when the computer is started

Disk based OS Takes up lots of Main Memory when loaded Vulnerable to corruption

Single User OS

A Single User OS is capable of supporting one user at a time

Layers of a Single User OS Command Language Interpreter File Management Memory Management Input/Output Management Process Management – the

Kernel

Kernel

I/O

MMS

FMS

CLI

Aims of Lesson 2

Last Lesson1. What is an Operating

System?2. Bootstrap Loader3. Single user OS4. Functions of single

user OS

Today’s Lesson1. Different layers in the

OS1. CLI2. FMS3. MMS4. I/O5. Kernel

2. Complete software questions on shared area

OS Layers

Think of the OS as a series of layers

This form of structure makes it easier to give software upgrades to particular areas Kernel

I/O

MMS

FMS

CLI

Command Language Interpreter

The CLI is the outer layer of the OS

This is the layer through which users communicate with the computer, e.g. providing the HCI Command Driven? Menu Driven – GUI? User-friendly – responds to input

with helpful error messages

File Management

The FMS layer makes sure the computer’s backing storage media is used effectively

Also known as the Disk Operating System (DOS)

The FMS organises files in a hierarchical filing system with files in directories and sub-directories

The FMS stores the physical address of files on backing storage

Aims of Lesson 3 Last Lesson1. What is an Operating

System?2. Bootstrap Loader3. Single user OS4. Different layers in the OS

1. CLI2. FMS

Today’s Lesson1. Different layers in the OS

1. MMS2. I/O3. Kernel

2. Research the following Utility Software, make a slideshow

1. Virus Checker2. Disk Editor3. Defragmenter4. Backup5. Emulators6. Converters, compressors and

expanders7. Installers/Uninstallers,8. Printer Drivers9. Email and Web Filters

Memory Management System

This layer of the OS controls where programs and data are placed in Main Memory

It keeps track of the amount of Main Memory available for programs and files

If insufficient space it sends an error to the CLI and this is passed on the user

The MMS allows multi-tasking with more than one program loaded into RAM at the same time

Input/Output Management

The input/output management layer or BIOS communicates directly with the peripherals and handles the transfer of data between the peripherals and processor

The I/O system is supplied by the computer manufacturer as it needs to be tailored to suit the particular hardware in use

The Kernel

The Kernel is the part of the OS responsible for handling interrupts

The Kernel manages the processes coming through the OS Example

Mr McAlpine gives the instruction to print Kernel receives this an passes the job to the I/O

system

Utility Software Utility software is a type of systems

software designed to perform an everyday task

Examples1. Virus Checker2. Disk Editor3. Defragmenter4. Backup5. Emulators6. Converters, compressors and expanders7. Installers/Uninstallers,8. Printer Drivers9. Email and Web Filters

Aims of Lesson 4 Last Lesson1. What is an Operating

System?2. Bootstrap Loader3. Single user OS4. Different layers in the

OS1. CLI2. FMS3. MMS4. I/O5. Kernel

Today’s Lesson1. Research the following

Utility Software, make a slideshow

1. Virus Checker2. Disk Editor3. Defragmenter4. Backup5. Emulators6. Converters, compressors

and expanders7. Installers/Uninstallers,8. Printer Drivers9. Email and Web Filters

Utility Software

Systems software required to perform a particular task

1. Virus Checker Software that detects the programming structure of a virus

and eliminates it Updates are often available to detect the most recent

viruses

2. Disk Editor Software that allows you to edit the surface of a disk,

bypassing the normal saving feature of the OS Disk clean up software may be used to delete

temporary files

Utility Software

3. Defragmenter The software gathers

scattered file fragments Improves performance by

reducing the distance the read-write head has to move

4. Backup Software used to

automate the process of making second copies of files

May also synchronise files

Utility Software

5. Emulators A program that allows one computer to behave as if it is a

completely different computer system

6. Converters Software used to change the file format of a data file

7. Compressors and Expanders Software used to reduce the file size e.g. Winzip

8. Installers/Uninstallers Where a wizard program is used to place or remove an

application or OS on to the hard disk

Utility Software

9. Printer Drivers A printer driver takes the

codes used in the document and translates them into the appropriate code for the printer you are using

10. Email/Web Filters Software that is often

used in school to monitor emails being sent or URLs that are being accessed

Aims of Lesson 5 Last Lesson1. What is an Operating

System?2. Bootstrap Loader3. Single user OS4. Different layers in the OS

CLI, FMS, MMS, I/O, Kernel5. Utility Software

1. Virus Checker2. Disk Editor3. Defragmenter4. Backup5. Emulators6. Converters, compressors and

expanders7. Installers/Uninstallers,8. Printer Drivers9. Email and Web Filters

Today’s Lesson1. Revision Quiz on Software

keypoints so far in software2. Standard File Formats

1. GIF2. JPEG3. TIFF

Standard File Formats

1. Graphic Interchange Format (GIF) Used for storing bit-mapped colour

graphics Uses 8 bits giving maximum of 256

colours per pixel Uses lossless compression making it

faster to load and transfer files Used to store line drawing with blocks of

the same colour Not suitable for photographic images

which lose quality if stored in 8 bit format

Standard File Formats3. Joint Photographic Experts Group (JPEG)

Uses lossy compression, cutting out data the human eye wont miss

Used for storing photographs Uses 24 bits per pixel representing over 16 million colours JPEG has range of compression rates

2:1, 30:1 Graphics saved as JPEGs are much smaller than the

equivalent saved as a GIF

4. Tagged Image File Format (TIFF) Used for high resolution bitmapped images TIFF is an uncompressed file format Used when a high quality image is required

Description of Suitable Software for Particular Tasks

1. Production of a Multimedia Catalogue A multimedia catalogue is a database of products or

items, which contains a variety of media, such as sound, graphics and video

2. Setting up a LAN in a School??

3. Development of a School Website??

Give me the characteristics of your chosen software and explain why you have chosen it

Selecting Software

1. Production of a Multimedia Catalogue Hyperstudio or Macromedia Director Features

Insert sound, videos, animations, bank of multimedia resources

2. Setting up a LAN in a School?? Microsoft Windows Server Features

Security, user groups, file, printer sharing

3. Development of a School Website?? MS FrontPage Features

GUI Interface, access to HTML, templates, sound, video, hyperlinks etc

Aims of Lesson 6 Last Lesson1. What is an Operating System?2. Bootstrap Loader3. Single user OS4. Different layers in the OS

CLI, FMS, MMS, I/O, Kernel

5. Utility Software1. Virus Checker2. Disk Editor3. Defragmenter4. Backup5. Emulators6. Converters, compressors and expanders7. Installers/Uninstallers,8. Printer Drivers9. Email and Web Filters

6. Standard File Formats1. GIF2. JPEG3. TIFF

Today’s Lesson1. Viruses2. Types of Viruses

1. File2. Boot sector3. Macro

3. Virus Actions4. Trojan Horses5. Worms

Virus

Virus A destructive piece of software that

attaches itself to files, reproduces, spreads and corrupts files or data

Classifying Viruses1. File Virus

This type of virus attaches itself to an application such as a game.

When you run the program, the virus instructions are also carried out

Virus continued

Classifying Viruses2. Boot Sector Virus

This type of virus infects the systems files that your computer uses each type you power up i.e. the OS

3. Macro Virus A macro is a legitimate set of instructions to

automate operations Hackers can create a destructive macro that may

attach itself to other documents and spread

Virus Actions

Camouflage Where the virus disguises itself to avoid detection by

adding fake instructions that look genuine Watching

Where the virus checks for a condition before carrying out destructive action , for example, waiting on a date or key press

Replication Each time the infected computer is run the virus

reproduces itself Delivery

The process of carrying out its destructive task such as erasing files or introducing loops to slow the system down

Trojan Horse

This is a piece of software that appears to be doing one thing but is actually secretly doing another job

A classic Trojan Horse activity is to pretend to be a disk defragmenter but actually deletes all your files

Aims of Lesson 7 Last Lesson1. What is an Operating System?2. Bootstrap Loader3. Single user OS4. Different layers in the OS

CLI, FMS, MMS, I/O, Kernel

5. Utility Software1. Virus Checker2. Disk Editor3. Defragmenter4. Backup5. Emulators6. Converters, compressors and

expanders7. Installers/Uninstallers,8. Printer Drivers9. Email and Web Filters

6. Standard File Formats1. GIF – 8 bit2. JPEG – 24 bit3. TIFF

Last Lesson1. Viruses2. Types of Viruses

1. File2. Boot sector3. Macro

3. Virus Actions4. Trojan Horses

Today’s Lesson1. Worms2. Virus Detection Techniques

1. Searching for Signatures2. Use of checksum3. Memory resident monitoring4. Heuristic detectors

Worms

A worm spreads from computer to computer via security holes in a network

Unlike a virus, it does not need to be attached to a file or program

Worms normally flood a network with useless traffic which halts communications

Virus Detection Techniques

1. Searching for Signatures Anti-virus software may have a table containing sections of

code which identifies a virus. It scans macros, programs, files etc looking for these virus

signatures

2. Use of checksum This technique scans an uninfected file and calculates a

checksum If it scans the same data again and the checksum is different

it knows the file has been infected

3. Memory resident monitoring This anti-virus software monitors all the computer’s activity,

for example, compressing files, modifying instructions etc. If it finds anything suspicious it brings up an error message

Virus Detection Techniques

4. Heuristic detectors This software looks for code that is triggered by time or

date events and for instructions that bypass the OS

Revision Quiz

1. List the 5 layers of the OS2. What is the name of the part of the OS that is stored on

ROM?3. Why do you not store the entire OS on ROM?4. What is the purpose of the CLI?5. Give 3 functions of the OS6. What is the name of the utility software that allows one

computer to behave as if it is another?7. Explain how a Defragmenter improves system performance8. Give 1 advantage of the JPEG file format9. Give 3 different types of viruses10. Describe a Trojan Horse11. Give 2 virus detection techniques12. Give 2 virus actions