2. Hardware and Software

All Past Paper Questions: https://docs.google.com/document/d/1AjL53GAhZXb_fa4mALsTHMoJZlIfAlF35uHH96iPWQ4/edit?usp=sharing

Computers

• fault tolerance

  • both
    • whether computer will repair itself if an error occurs
    • a computer can operate even if components fail
    • without system downtime
    • computers operating quality can be reduce
      • but it does not fail completely
    • whether when a hardware component fails, is it hot swappable
  • super computer only
    • will run two copies of software
    • if one fails, the second copy will start

• heat maintainance

  • computers generate a lot of heat
    • due to quality and quantity of processors
  • it can be a problem when it overheats
  • to address this issue
    • good cooling systems are needed
      • can air cool with an AC - expensive
      • can water cool - cheap, efficient
      • build datacenter in a cold part of the world, eg: greenland.

Mainframe Computers

• description

  • have hundreds of processor cores
  • all cores share one OS
  • mainframes use parallel processing
  • can process a large number of small tasks at same time

• advantages

  • have faster processing
    • can perform hunders of MIPS
  • have high value of MTBF (Mean Time Between Failures)
    • so, less downtime
  • have greater fault tolerance
    • can transfer processing from one core to another
    • so, hardware and software updrades can occur while the system is still running
  • they can run different OS
    • so, can handle different types of database
  • they are more secure than most other types of computer
    • as they use complex encryption system

• disadvantages

  • very expensive to buy
    • some are using cloud instead of this
    • due to this being too expensive
    • maintainance
    • cost to people who manage this
    • software costs
    • cooling costs
  • need large rooms
  • generates a lot of heat,
    • need good, expensive and complex cooling systems

• why used to produce census?

  • mainframes has a,
    • high speed of processing data
    • scalable
    • reliable
  • amount of data to be processed is very large
  • as countries have a lot of people
    • it also keeps on increasing
    • census processes & produces more data
  • more poweful machines are needed as more data is added

• transcation processing systems

  • performance is meausured by the number of transactions it can process in a given period of time
  • must be continously available
  • must able to maintain integrity of data
    • and overcome hardware and software problems
  • it must also be possible to individually upgrade hardware and software components without suhtting down the system
  • there should be controlled access, allowing only authorised users to use the system

• performance metrics

  • used to measure performance speeds of computers/processors
  • can be unreliable as the complexity of instructions can vary according to which benchmark program is used
  • MIPS are used for integers
    • Million Instruction Per Second
  • measured in millions
  • used when measuring performance of computers involved in running application software
  • do not take into account the input/output speeds

• RAS

  • Reliability, Accessibility and Serviceability
  • describes the robustness/durability of a mainframe computer
  • Realiability
    • chance of the system behaving as intended
  • Accessibility
    • mainframe being operational at all times
  • Serviceability
    • can be easily fixed within a short period of time
  • if there is a failiure
    • reliable
    • will use alternative methods to carry out tasks
  • software is reliable
    • highly tested
    • and updates are made quickly to fix problems
  • MTBF (Mean Time Between Failures) is long for mainframes
    • mainframes give months/years of systemd owntimes
  • when unavailable (due to failiure)
    • mainframe is unavailable for a very short time
  • spare components (CPUs) are inlcuded in mainframes
    • if one fails, nother takes over
  • mainfram can determine why failiure occured
  • enables hardware and software components to be replaced without affecting mainframe's operations
  • can be serviced while the system is still running

Super Computers

• description

  • can have more than 100,000 processing cores
  • use massively parallel computing
  • each core has it's own OS
  • use more than one GPU

• effectiveness / features

  • have a limited lifespan of just a few years
  • and will need replacing / repairing
  • carries out complex calculations
  • can use complex maths formulae
  • can handle a large amount of items of data at same time
  • fasted data processing computers
  • most expensive to buy
  • each processor has it's own operating system
  • use massively parallel processing
  • more powerful compared to mainframes
    • can be upto 1000 times faster
  • can include scientific rules
  • some tasks do not require super computers
  • overheats, hard to keep it cool
  • as the task is not complex, so, it would be a waste of time

• performance metrics

  • used to measure performance speeds of computers/processors
  • can be unreliable as the complexity of instructions can vary according to which benchmark program is used
  • (M) FLOPS are used for real/floating point numbers
    • Floating Point Operations Per Second
  • measured in quadrillions and higher
  • used where complex (scientific) calculations need to be carried out
  • to not take into accuont the CPU's clock speed, bus speed and RAM available

• weather forecasting

  • powerful enough to carry calculations required
  • can process huge amounts of data
  • based on use of very complex/scientific computer models
  • a advanced three-dimentional model of earth has to be created
  • and large number of complex calculations are carried
  • but first, data should be collected
    • records of previous weather conditions
      • weather measurements from weather stations
      • observations from satellites
      • information from ships & aircrafts

• climate research

  • many variables are collected
    • using sensors, eg:
      • rainfall, temperature, humidity, etc...
  • large quantity of data is processed
  • complex calculations are carried out
  • shows historical trends of different variables over a long time period
  • complex maths formulae are used to describe how different parts of climate works
    • computer models based on these are used to predict how the climate will change
    • these models will include several scientific formulae
  • model will give you the best guess

Cloud Computing

• cloud storage
  • advantages
    • paying a low monthly fee
    • has no physical precense, so, takes no space
    • can backup data automatically
    • syncing ensure files are automatically updates across all devices connected
  • disadvantages
    • data is in hands of third party
      • so, less secure
    • providers can be transient
      • resulting in possible data loss
    • only as reliable as the user's internet connection
    • some may charge a cheap initial fee, but may increase prices later
    • users are at risk of not having data stored in compliance with government regulations if the physical storage location resides in a different country

Software

• Software are programs used to direct the operation of a computer and related hardware

FULL DIRAGRAM IMAGE HERE

System Software

• directly operates the computer hardware

• both compiler and interpreter converts high level programming language to a lower level instructions

• designed to run a computers hardware and application programs

• managed computer hardware

• provides a platform the application software to run

• general purpose

• takes care of memmory management of the system

• Question

Compilers

• features

  • translates the whole porgram as one complete unit
  • creates an executable file
  • is able to report on a number of errors in the code after compilation
  • does not need to be present in order to run the program (compiled executable)
  • can optimize source code to run as fast or as efficiently as possible
  • often produces a seperate object code program
  • converts high level instructions to machine language
  • entire file is compiled before execution
  • list of errors is created after the compiltation process
  • compiled program is directly executed using the machine code
  • has to be recompiled even if the smallest change is made
  • difficult for hackers to modify compiled code

• advantages

  • once compiled, translation software is no longer needed
  • runs faster (fast execution)
  • quicker process than interpreting
  • improve security for programmers
    • making it harder to copy code
    • fewer risks of copyright infringement

• disadvantages

  • can only be used in one OS
    • target audience may run many OS
    • might need to use an interpreter
  • has to be recompiled even if the smallest change is made

• usually, compiles with native compiler

• to run in another platform

  • can cross compile
  • will run more slowly
  • produces more errors and mistakes

Interpreters

• how it works?

  • translates each line of source code inito an intermediate stage and then executes that line / statment
  • translation happens line by line (one instruction at a time)
  • reports on errors as lines of source code are processed
  • an interpreter has to be resident in memmory in order for the program to run
  • only a few lines of the program need to be in memory

• features

  • translates each line of source code inito an intermediate stage and then executes that line / statment
  • reports on errors as lines of source code are enetered
  • only a few lines of source code needs to be in memory at any one time
  • some interpreters execute code within a virtual machine
  • these have been designed to disallow code from directly accessing the data computer
  • converts high level instructions to an intermediate form (called "object code")
  • translates one statment at a time
  • stops translating after the first error
  • interpreter has to be in memmory for the program to run
  • can be modified at runtime (changing functions)

• advantages

  • when need to run on many OS
    • can maintain one version of the source code
  • less time will be spent on maintainance
    • when updates are needed
  • easier to debug the program
    • as errors are highlighted
  • it can use up less memory than a compiler
    • as only a few lines of source code are in memory at given time
  • less likely to crash the computer
    • as the code can run in a virtual machine (like JVM for java)

• disadvantages

  • translation software may need to be kept upto date
  • interpreted programs run slower than compiled programs
    • as they have to be interpreted every time they are run
  • interpreting a program is much slow process than compiling
    • as it stpos every time an error is encountered
  • source code is easier to convert by fraudulent users
  • makes it much easier to copy the program

Linkers

• a linker takes one more more object files and combines them into a single executable file

• advantages

  • programs can be written in modules
    • requires less RAM
    • saving cost of memmory
  • whole program and compiler dont need to be in memory at the same time
    • requires less RAM
    • saving cost of memmory
  • several programmers can work on seperate modules
    • saves time (compared to one person writing the whole code)
  • if there is an error, only that module has to be fixed

• disadvantages

  • variable names can cause problems
    • the same variable may have been given different variable names in different modules
  • documentation has to be more detailed
    • so takes longer to write

All

• why we need all of these?
  • many programming languages allow the wiritng of different peices of modules seperately
  • programming tasks are simplified as large programs can be broken into smaller manageable pieces
  • the linker is used to put all the modules together
  • without the comiler, the linker would have no object files to combine

Operating systems

• tasks carried out / purpose

  • allocates memmory to software
  • sends instructions to printers
  • recognizes and responds to input devices
  • opens and closes files on devices
  • does file management
  • multi-programming systems allocate equitable processing time to each task
  • sends error messages if an error
  • hanldes user logins
  • handles file permissions
  • provides the interface between a user and the computer
  • manages hardware resources
  • responsible for handling errors

• purpose

  • multi-processing OS is when system has more than one processor
  • multi-tasking OS allows more than one program to run at a same time
  • multi-tasking OS allocates sufficient processor time to each program
  • multi-threading OS allows different parts of a single program (process) to run at the same time
  • real-time OS allo the computer to respond to input instantaneously
  • distributed OS allows data to be stored on a number of computers in different locations

Device drivers

• purpose
  • it controls a device attatched to the computer
  • without required device driver, corresponding hardware device fails to work
  • it is the interface between OS and hardware device
  • tells the OS how to communicate with hardware device
  • upon installation, it detects and identifies peripheral devices
  • handles translation of requests between device and computer
  • ?? defines where outgoing data must be stored before it can be sent ??
  • different OS may send different instructions, driver translates them to what printer can understand

Utility Software

• programs that help maintain the computer
• performs a very specific task, usually, managing system resources
• OS can contain a number of these utilities out of the box
• why it is needed?
  • to keep computer free from viruses
  • to make files contiguous
  • ?? needed to improce performance by allocating memmory ??

Anti Virus Software

• note: viruses are also a type of software
• to remove viruses
• scans computer for viruses
• software used to prevent, detect and remove malicious software (called 'malware' for short)
• can protect from:
  • malicious browser helper objects,
  • browser hijackers,
  • ransomware,
  • keyloggers,
  • backdoors,
  • rootkits,
  • trojan horses,
  • worms,
  • adware,
  • spyware,
  • etc...
• signature based detection
  • compares the contents of file
  • to its database of known signatures
• heuristic-based detection
  • detects malware vased on characteristics typically used in known malware code
• behavourial based detection
  • based on behavourial fingerprint of the malware at runtime
  • is only able to detect malware after they have start malicous actions
• sandbox detection
  • based on behavourial detection
  • but it doesnt detect behavourial at runtime
  • it executes the programs in a virtual environment
    • logging the actions performed by the file
• gives the user options to delete or qurantine the files
• does backgroudns cans of downloads and attatchements
• prompt the user to scan newly plugged in

Data Compression

• to reduce storage file size of a file
• encoding information using fewer bits than the original representation
• two types
  • lossless compression
    • reduces the number of bits
      • by identifying repeated patterns
      • and encoding them in special ways
        • eg: Run Length Encoding (RLE), Huffman Encoding
    • same quality
    • information is not lost
  • lossy compression
    • reduces the number of bits
      • by identifying unncecessary information
      • and removing them
    • reduced quality
    • information is lost

Disk Defragmentation

• removes non-contiguous spaces on disk
• organizes contents of the disk into smallest number of contiguous blocks
• it is re-arranging the files stored on the disk
• attempts to create larger regions of free space using compaction
• some defragmentation utilities try to keep smaller files within a single directory together
• the movement of the hard drive's read/write heads over different areas of the disk when accessing fragmented files is slower
  • compared to accessing the entire contents of a non-fragmented file sequentially
• will make the data retrieval easier and quicker

Disk Formatting

• prepares a data storage device for initial use
• organizes the tracks on a disk into sectors
• a new disk medium is fully prepared in order to store files
• the first stage is low-level formatting followed by
  • partitioning which makes the data storage device visible to an OS
  • followed by high-level formatting which generated a new file system
• low-level formatting divides disk surface into tradcks, secors and cylinders
  • done by magnetising disk areas using write heads
  • tracks are numbered s tarting from 0
  • when the head goes from one treack to next, it leaves a gap
  • each track is organized into numbered sectors, starting at 1 and seperated by gaps
  • the purpose of low level formatting is to prepare the disk surface to reveive data
• high level formatting
  • creates a file system on the disk
  • this allows the OS to use the disk space to store data and access files

Backup Software

• to make copies for future use
• creates additional copies of all data in the computer
• backed up data is available incase of data loss, eg:
  • lost to a ransomware
  • accidental deletion
• can use copies to restore original contents
• asks use to enter type of backup
  • full
  • incremental
  • differential
  • etc...
• can backup automatically, on scheduled time, set by user
  • backup process will consume disk resources
  • making the computer slow
  • so, should make backup at convenient time
  • eg: night time
• taking backups regularly
  • will prevent the chance of data loss
• asks if you wish to restore the backup
• asks if you wish to verify the backups
• asks frequency of backups (how often they should take place)
• ask which medium the user wishes to store
• select where to save the backup
  • target location
  • it should be secure
• can also encrypt the backup
  • provides more security

File Copying

• creation of new files, which has the same contents as an existing file

Deleting Files

• removing a file from the computer's file system
• most OS keeps track of where files are on hard disk using pointers
  • each file and folder on a hard disk has a pointer that tells the OS
  • where the file's data ends and begins with
• when a file is deleted,
  • OS deletes pointers
  • marks secotrs containing that file as available
• its considered that files are no longer present in hard disk (considered as free space)
• uses a file allocation table (FAT) to store the location of files on the disk
• the delete utility just deletes the reference of the index in the FAT
• until OS writes new data, deleted files are still recoverable
• recovery programs can scan for deleted files and restore them
• if file is partially overwritten, can only recovery half of that file
• file recovery pointers work by reinstating pointers
  • reinstating the index in FAT

Application Software

• group of software designed for the end user
• uses computer to perform specific tasks
• not required to run the system
• its user specific
• interface between user and system software
• eg: spread sheet software, word processing software, database software, animation software, video editing software, etc...

Word Processing Software

Spreadsheet Software

• Click here to learn more

More Stuff

• word processing software vs spreadsheet software

  • similarities
    • allows users to enter numeric and text data into a report
    • can perform calculations using formulae and functions
    • let users format text with fonts, colors, etc...
    • allow importing of graphics like images and charts
    • includes ability to save files in many formats
    • have spelling and grammar checking
    • has search and replace functions
    • have page formatting options, headers, footers, etc...
  • differences
    • text alignment and page margins are handled in different ways
    • spreadsheet
      • users can create models
        • create "what is" scenarios
      • uses cells, rows and columns to hold data
    • word processing
      • can produce reports & mail merge
      • only has basic functions to aid calculations
      • doesnt restrict where data can be entered (no cells)
      • includes word count feature

• cross application support (why cannot import word file to spreadsheet file)?

  • word processing files are word processing file type
  • spreadsheets are a different type of files
  • to overcome issues,
    • convert word processing file to generic file format
  • save word processed file as .txt or .csv
  • then, he will be able to open it

Off the Shelf Software

• description

  • software that is ready-made and already exists
  • it is available to all bussiness and companies
  • it is owned by a company that created it
  • has to adapted to fit the bussiness that has purchased it

• advantages

  • cheaper, as mass produced
  • available straight away
  • testing can be righteously carried out by developers, so, less bugs
  • many sources of support
    • web forums
    • comminity support
    • wiki's
    • includes helplines with operators who have already dealth with many problems, so, experienced
  • will have been used many times before companies buy it, so any bugs will have been identified/reported and fixed

• disadvnatages

  • difficult to adapt to particular use required by the school
  • has bloated, distracting, unwanted extra features
  • may not be compatible with current systems and infrastructure
  • some very specific functions may not be available

Custom Written Software

• description

  • software that is specially developed for a specific company
  • it is made to accomodate that customer's particular preferences and needs
  • written by programmers to solve specific problems
  • owned by the bussiness that commisions it
  • is it made from scratch

• what

  • software created for defined purposes
  • does not need to be adapted for use
  • any built in settings can be changed
  • programmer will ensure device compatibility
  • if software doesnt meet companies requirements
    • programmers with have everything fixed
    • eg: ability to copy software to several devices
  • they will not have unncecessary bloated features
    • the usually takes less space than off the shelf software
      • so, less expensive storage costs
  • company will own the custom written software, so, they can sell it to others

• advantages

  • designed specifically for client's requirements
  • there will be no unncessecary features
  • it does not have to be adapter for use
  • programmers are available to make any changes required
  • programmers will ensure the software is compatible with company devices and infrastructure

• disadvantages

  • costs more to pay programmers to write more
  • testing is limited to only what programmers think is required
    • based on how they think the software will be used
    • not thoroughly tested
    • so, can have a lot of bugs
  • support is limited to team of programmers only
  • can take a long time to develop the software

Mental Model

• explanation?

  • based on bliefs, not facts
  • what user will describe as what they need
  • deisgner must produce UI to match user's thoughts
  • model of what users know/think about a system
  • users create mental models very quickly (even before using any software)
  • comes from prior experience of user
  • designers should stick with this, or it will be hard for users
  • user will take less time to learn (if product is similar to his mental model)
  • will provide the user with transferrable skills
  • training can be changed to fit user's mental model
    • to fit the design of the interface

• advantages

  • easier for user to use UI
  • takes less time to learn how to use the UI
  • interface is predictable as it will match their requirements
  • user will gain transferrable skills
    • so, easier to use other apps

• disadvantages

  • range of definitions of what constitutes a mental model
    • can cause confusion
    • resulting in inaccurate results
  • lack of clear methodology to use
    • leading to a bias
    • based on designers own intepretation
  • little research
  • maybe difficult to match user interface to user's perception of real world

Conceptual Model

• actual model that is given to the user
  • through the user interface
  • of the product

User Interface

• What to consider when creating a custom user interface?
  • how color is to be used
    • (color palettes)
    • choosing color combinations
  • layout
    • positioning elements
    • to ensure readability
    • increase font size to emphasize importance of certain elements
  • only display information the user needs
  • decide which controls will be required
  • which navigational aids are required
    • navigation bar (top)
    • side bar
    • breadcrumb

User Interfaces

• CLI & GUI

  • more accurate & reliable
  • user must be sitting infront and controlling it
  • require actions to deliberate

• GBI & Dialog Interface

  • for handicapped users (physical disabilities) who cannot use keyboard and mouse
    • or control their limbs accurately
  • more expensive to develop
  • for reasons of hygene, not even a doctor is allowed to touch the device
    • then, use gestures or dialog to control device
  • not suitable for safety related stuff
    • if in emergency
      • (GBI) gesture might not get registered
      • (DI) 'stop' like words might not be identified properly

CLI

• Command Line Interface

• prompt appears in screen

• after which the command is typed

• used by advanced computer users

• less likely to change over time

• uses less memmory

• requires user to learn many commands

• processing is faster than others

• doesnt require graphics or high-resolution monitor

• disadvantages

  • user should learn many commands
  • can be slowed to input, for new users
  • long lines of text needs to be entered, instead of a few mouse clicks
  • commands can be more difficult to edit
  • more difficult to multi task
  • very basic, and can be more of a strain to user's vision
  • more likely to make mistakes when typing commands

GUI

• Graphical User Interface
• involves the use of WIMP
  • Windows, Icons, Menus, Pointers
• layout
  • sensible use of white space
  • information that needs attending to immediately should always be displayed in prominent position
  • a consistent use of screens
  • must not overload the user with information
  • should follow the house style of the company using it
  • information should flow in a logical order to the user

Dialog Interface

• Dialog Interface
• stuff?
  • requires a microphone
  • can speak into a microphone to control the device
  • requires training session with user
  • unreliable when there is a background noise
  • gives hands free control
    • can use when driving, can use voice instead of driving with one hand

GBI

• Gesture-Based Interface
• stuff?
  • can perform a gesture to control the device
  • quicker way of initating a response from a device
  • less effective when several users or with background movement
  • gestures can be taught through manuals
  • unreliable when used in the dark
  • bad when driving, will have to drive with one hand while doing gestures with the other hand
  • unintentional gestures might be registered
  • very reliable as most users have similar gestures for communicating
  • requires a line of sight (unlike dialog interface)

Hardware

• Another name for physical parts of the computer
• collection of physical components

CPU

• parts

  • Arithmetic Logical Unit (ALU)
  • Control Unit (CU)
  • Memmory
  • tends to be contains on an intergrated circuit chip called a microprocessor

• function

  • CU fetched instrctions from main memmory
  • decodes instructions
  • executes instructions
  • all input data are transferred via CPU's memmory
  • memmory stores instrctions as well as data
  • data is stored in the CPU memory, whilst a calculation or instruction is being carried out
  • input data are transferred to the ALU for processing
    • ALU makes use of 4 basic functions: +, -, *, /
    • ALU uses certian logic operations such as comparisons, selections and matching

Mother Board

• description
  • the main printer circuit board of a computer
  • connects the main components of a computer
  • contains
    • mass storage interfaces
    • serial and parallel ports
    • usb ports
    • network ports
    • expansion slots (PCI, PCIe)
    • controllers required to control standard peripheral devices
    • southbridge
    • connections for attatching additional boards
    • bios
    • CPU socket
    • RAM slots

Sound Card

• description
  • manipultate and output audio
  • manipulate sounds stored on disk
  • recieve sound from input from a microphone
  • output sound trhought speakers connected to the bord
  • nearly all sound cards upport MIDI, a standard for represeting audio electronically

Input Devices

• Touch Pad

  • used to simulate the behvaiour of a mouse when using a laptop

• Keyboard

  • or 'number pad' - whats used in supermarkets
  • type in values
  • advantages
    • experiences users can enter data more quickly
  • disadvantages
    • difficulty of entering amounts other than selecing numbers using a mouse
    • data is slow to enter (compared with DDE)
  • using the keyboard
    • can use CTRL + other keys to save, print, copy, paste, cut, etc... (keyboard shortcut)
    • can use arrow keys to navitage through text
    • can use tab key to indent, delete key to delete forwards, backspace to delete backwards
    • can use the alphbetic keys and number keys to type content
  • in a shop, if product bar code is damaged, it cannot be input

• Touch Screen

  • both input and an output device
  • could be used to eneter amounts
  • quicker to enter data than using a mouse
  • may cause screen to be stained and make viewing difficult

• RFID reader

  • reader can be used to enter details from passport / bank card
  • quicker than manually entering data
  • readers are expensive to buy initially

• in Bank Cards (credit cards / debit cards)

  • uses a chip reader to read cards
  • reliable than reading a magnetic stripe
  • quicker than typing details from the card
  • contactless card readers speed up transactions as no PIN is required
    • in many countries, there is a maximum amount of money allowed to be charged with this.
  • chip and pin-reader
    • reads details from bank cards
    • more secure
    • more reliable than rading magnetic stripe
    • quicker than typing details from the card

• Bar Code Scanner

  • used to read bar codes from products

Output Devices

IMAGE HIERARCHIAL

• Monitor

  • results are produces instantly
  • graphs / diagrams / figures are represented more accurately
  • scroll through results easily (instead of turning pages)
  • need to be infront of monitor to view the output

• Printers

  • easier to annotate printouts taken

  • printouts can be transported and viewed anywhere

  • may skim on whats on-screen.

    • so, more likely for errors to occur

  • Dot Matrix Printer

    • not very clear comparatively

    • uses continous stationery

    • slow to print

      • if busy, will cause queues of people waiting to print

    • less risk of this running out of paper

    • will have 'noise' in print (bad)

    • cheaper to run

      • ink ribbon is cheaper than catridges or toners

    • advantages

      • can use carbon copy paper (requires less filling of the sheet feeder)
      • could use continuous stationary
        • which would require less human interction
        • doesnt run out of paper very quckly
      • ink ribbon lasts longer and is cheap
      • when ink runs out, print gets fainter, but is still legible

    • disadvnatages

      • striking of heads cause a lot of noise
        • distracting in office envrionments
      • quality of output is not very good
        • 240dpi, but inkjet does 1200dpi
      • slow output
      • to buy a dot matrix printer is very expensive
      • has a more limited character set

  • Inkjet Printer

    • high quality tickets
    • slow to print
      • (all copies, including the first copy)
      • if busy, will cause queues of people waiting to print
    • will need to change catridges more frequently
    • when ink runs out, prinout is less legible

  • Laser Printer

    • quiality of print will be good
      • can see it clearly
    • takes time to produce the first copy
    • does not have tio change toner as often as inkject catridges

Storage Devices

• Exam Question:

Primary

• quicker than secondary

• ROM content is sometimes copied to RAM and subsequently read from RAM

• very fast access times

• no moving parts

• stores data in use and stores data for later user

• RAM

  • Random Access Memmory
  • stored information for short term usage
  • volatile: data is deleted once power is lost
  • stores active program data
  • ?? faster than ROMs ??
  • used by computers for storing data during computing processes
  • stores active program data
  • can both read and write

• ROM

  • Read Only Memmory
  • cannot be changed, only read
  • non volatile: data is retained even when power is off
  • stores permanent computer instructions
  • (to store bootup instructions) contains instructions for the computer to start up when it is turned on again
    • stores bootup instrctions - that will activate the hard disk
  • to store software that is unlikely to need frequent updates

Secondary

IMAGE HIERARCHIAL

• portable

• non volatile

• stores data for later use

• CPU can both read from and write to data

• Optical Drive

  • uses laser to burn dark pits into medium
  • each dark pit is a binary digit
    • if there is a pit: 1, else: 0
  • Advantages
    • faster data access times (comapred to tape)
    • more viable when theres large variations of temperature
  • Disadvantages
    • not very portable (compared to tape)
    • more suspectible to damage when handling
  • types:
    • CD
    • DVD
      • stored upto 8.7GB max (DVD - Double Side - Double Layer)
    • Blu Ray Disk
      • single blu-ray stores upto 128GB max
        • can store high quality videos
      • more expensive
      • costs less to buy per unit memmory
    • note:
      • BR drives can read DVDs
      • DVD drives cannot read BR dicsts

• Magnetic Media

  • aka Tape
  • small areas of tape are magnetized to represent 1/0
  • have surfaces coated with magnetically sensitive material such as iron oxide
  • Advantages
    • costs less per unit storage
      • so, more cost effective (for large companies)
    • stores more data
    • appropriate for server backups
    • less suspectible to damage when handling
      • because its completely encased
    • hardest to hack into
  • Disadvantages
    • costs more per tape
    • gets curropt if placed near a magnetic field
    • slower access speed
      • as data is stored sequentially
      • when getting data, should start at beginning and start finding
      • not very silent
        • it also has moving parts

• Hard Disk Drives (HDDs)

  • have surfaces coated with magnetically sensitive material such as iron oxide

  • Advantages

    • higher storage capacitie
    • cost less per gigabyte
    • lasts longer

  • Disadvantages

    • consists of various moving parts
      • more suspectible to damage and shock / more prone to failiure
      • more pront to mechanical failiure
    • access speed is limited
      • depends on how close the data is to the read/write heads
    • loud, have whirring sounds due to moving parts
    • high power consumption

  • How it works? & Parts:

    

    • HDDs consists of several platters, which are individual disks
    • each surface of a platter has it's own read/write head
    • the read/write heads move across the platters
      • stoppping only read data from or write data to the surface
      • it never touches the surface
    • each surface is divided into several tracks, which are in the same position on each disk
    • the track on the top platter together with the tracks exactly below it, form a cylinder
    • each track is divided into sectors

• Solid State Drives (SSDs)

  • uses electric circuits (NAND flash)
  • stores data with an electrical charge
  • Advantages
    • have faster transfer rate
    • have quicker boot ups
    • can have almost instantaneous data access ()
    • all parts of SSD can be accessed at once
    • use less power at peak load
    • energy efficiency can deliver longer battery life in laptops
    • no moving parts, so, SSDs run silently
    • data can be accessed at once (specially thanks to the DRAM cache)
  • Disadvantages
    • low storage capacities
    • costs more per gigabyte
    • doesn't last long
      • NAND flash used in SSDs can only be used for a finite number of writes
    • choices and availability is limited

• HDDs vs SSDs

Feature	HDD	SSD
Storage Capacity	Higher storage capacities	Lower storage capacities
Cost per Gigabyte	Costs less per gigabyte	Costs more per gigabyte
Durability	Lasts longer	Doesn't last as long
Shock Resistance	More susceptible to damage and shock	No moving parts, so more shock-resistant
Access Speed	Limited access speed	Faster transfer rate, quicker boot ups
Noise	Loud, with whirring sounds	Runs silently
Power Consumption	Higher power consumption	Uses less power at peak load
Energy Efficiency	Lower energy efficiency	Better energy efficiency, longer battery life
Availability	Widely available with more choices	Limited choices and availability
Lifespan	Consists of various moving parts	Finite number of writes due to NAND flash

• Pen Drives
  • used to store data that is to be transferred
    • from one computer to another
    • because of ease of portability

---

Other

---

• Pg 39 - 2019 March 12 - 1 (to Database)

Software Stuff (to Database)

• NOTE: THIS BELONGS TO THE 'DATABASE' PART OF P1

• generic file format

  • description
    • one which will be recognizable to most software packages
    • if a software packages does not recognize, file is update to load
  • examples
    • .txt (text): can be loaded by most word processing software
    • .csv (command seperated values): can be loaded by most spreadsheet software
      • description
        • a text file
        • with data (including empty data)
        • seperated by a delimiter
          • a comma/',' is the default delimiter
      • why used by spreadsheet software?
        • smaller in size
        • so, less processing time
        • can be opened by many applications
        • data can be exchanged easily
          • among different spreadsheet software
          • among different computers & operating systems
        • its human readbale
        • easier to edit manually
  • why use text file instead of using word processed file?
    • file size is smaller
      • takes less storage space
      • so, has small processing time
    • text format doesnt need to buy license / software
      • eg: of word processing software
    • can be opened by more applications
    • data can be exchanged among different OS / Computers
    • word processing software has many versions
      • one may not support documents made with another verison
    • its human readable and easy to edit manually
    • disadvantages
      • no distinction between text and numeric values
      • documents will have no formatting
      • cant embed images / graphics / videos
      • cannot have tables
      • resulting layout may make it difficult to read

• propietrary software

  • software that is owned by an individual or a company (usually the one that developed it)
  • there are almost always major restrictions on its use
  • a software vendor delineates the specific terms of use in an end-user license agreement
  • its source code is almost always kept secret
  • usually covered by copyright which provides a legal basis for its owner to establish exclusive rights
  • usually created by a company
    • with secret (proprietary) encoding scheme
    • so, it can be decoded only using software of company

• open source file formats

  • description
    • can be used and implemented by anyone
    • an open source file format can be used by both propietrary and FOSS
    • also called free file formats if they are not covered by any copyrights
    • so that anyone may use them at no monetary cost for any desired purpose
    • can be opened by most types of software
    • there is a published speicifcation for storing digital data,
      • usually maintained by a standards organization
    • can sometimes be amended without violating of copyright laws
    • provides a standard file type
    • can work with different software without the need to have the same software
  • why need this
    • not everyone can afford proprietary software
    • when transferring from one device to another,
      • other devices may not have compatible software
    • archived proprietary files maybe difficult to read by new software

Web Conference (to Digital Divide)

• NOTE: THIS BELONGS TO THE 'DIGITAL DIVIDE' PART OF P1

• how to setup

  • answer 1
    • send emails to every person being invited informing them of the conference
    • he sends log in details to users
    • uploads any necessary documents for the meeting
    • sends a link to the website
    • enter his username and password (obtained from the provider)
    • select a start time and end time
    • in the meeting area, type an agenda
    • using the software select participants
    • select appropriate meeting space/room
    • select those participants who can enter the room
    • choose those who can be presenters
      • and who can manage the meeting
      • limit participation of participants,
      • disable messaging,
      • disable camers
  • answer 2
    • setup equipment and software
    • agree a date and time
    • send reminder to participants before they start
    • send invitation link, with meeting password
    • adjust webcam so that can be seen
    • create and enter virtual rooms
    • share documents with appropriate software
    • upload any necessary documents for the meeting
    • sends a link to the website
    • enter his username and password
    • using the software, select participants to accept in to the meeting
    • select appropriate meeting space/room
    • select those who can enter the room
    • limit the participation of participants, mute, disable messaging / camera, etc...
    • communicate by speaking into a microphone and looking at the webcam

• hardware required

  • server to handle video conferencing software
  • laptops/devices for each participant
  • microphone to speak to (sound - input)
  • speakers to hear (sound - output)
  • large monitor to see all participants
  • cameras/webcams to input pictures
  • router to connect to internet / network

Web Authoring (no idea yet)

• using web authoring software instead of html?
  • advantages
    • do not have to spend time learning html
    • do not need to have web development knowledge/skills to make a functional website
    • can make websites with basic clicking and typing
    • writing html takes much longer
    • most are WYSIWYG editors
  • disadvantage
    • limits the users options as a designer
    • they only rely on templates with limited options
    • depening on what web authoring software package you use
      • they might not even different features
    • software may make user reliant to it
      • if software breaks, can no longer develop the site
    • learning html means sites can be built from any environment with basic text editing software
      • eg: notepad (most basic) to intelliJ webstorm ide (advanced)

Encryption (to Security)

• NOTE: THIS BELONGS TO THE 'SECURITY' PART OF P1

• how encryption stores data stores on a hard disk?

  • can use either symmetric or asymmetric encryption
  • can be through the use of public and private keys
  • causes data to be scrambled
  • requires an encryption key to encrypt
  • requires a descryption key to decrypt
  • resusls in data which is not understandable
    • even if read by someone else, it will have no meaning

Inference Systems (to Expert Systems)

• NOTE: THIS BELONGS TO THE 'EXPERT SYSTEMS' PART OF P1

• how inputs are used to prodice diagnoses

  • finds possible diagnoses by using a form of reasoning
  • the inference engine uses the data or facts in knowledge base (to reason through the symptoms)
  • the reasoning involves forward chaining, backward chaining, or a combination of both
  • compares symptoms to those in the knowledge base
  • uses the rules base of IF...THEN... rules
  • also, write the description of forward chaining and backward chaining