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Computer Literacy study notes (F2 Final Exam)
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CL.md 

                            COMPUTER LITERACY
                           ===================

                              Revision Notes
                            Final Examination







































                            Name: __________________________

4 Health Risks

4.1 Health Risks of Computer Use

Computer Vision Syndrome (CVS)

  • Symptoms

    • Eye strain
    • Blurrred Vision
    • Headache

  • Causes

    • Looking at screen for too long.
    • Lowering rate of blinking due to concentration on a near screen.

  • Resolution

    • Avoid reflection. Avoid placing screen by winder.
    • Use a filter to reduce screen brightness.
    • Wear protective glasses to filter blue light.
    • Place screen slightly below eye level.
    • Blink eyes more frequently

Repetitive Strain Injury (RSI)

  • Symptoms
    • Stiff shoulders
    • Joint pain
  • Causes
    • Incorrect posture
    • Sitting in the same place for too long
    • Repetitive motion of some body parts
  • Resolution
    • Maintain proper posture
    • Take a 5-10 min break every 30-40 mins

4.2 HR of Smartphone Use

Posture Problem

  • Symptoms
    • "Smartphone Pinky", "Cell phone elbow", "Text claw"...
  • Causes
    • Overuse of smartphones.
    • Holding phone improperly for too long.
  • Resolution
    • Hold phone in different postures regularly.
    • Avoid pressure on fingers.
    • Take a break.

Vision Problem

  • Symptoms
    • Eye strain
    • Blurred Vision
  • Causes
    • Staring at small screen for too long
    • Using phones in bed or dark environment
  • Resolution
    • Take a break
    • Use phone under sufficient light

4.3 Minimizing health risks

Posture

  • 40-60 cm
  • 90 degrees
  • Spine staight
  • Chair with wheels
  • Wrist-rest
  • Place screen directly in front of body

    +-+
    | |                  /////////
    | | <- 40-60cm ->    //     /
   /| |                 /_      /
  / | |                   \   /
 /  +-+                    /  | <- 90 degrees
/___          ( )============ | ||
+===================+           || <- Ergonomic chair...

Breaks

  • 10 sec break / 10 mins
  • 2-5 min break / 30-60 mins
  • Use software to remind taking a break (BreakTimer...)

Ergonomic Products

  • Ergonomic keyboard / mouse
  • Ergonomic chair
    • Adjustable backrest height
    • Adjustable armrest height
    • Adjustable seat height
    • ...

5 Intellectual Property Rights

5.1 Copyright

Copyright is automatically given to the author after creation of work. All creations are protected by law, and there is no official registry.

Hong Kong Copyright Ordinance applies to literature, movie, music, TV broadcast... Anyone who wants to use the work must seek authorization from owners.

5.2 Software License

  1. Commercial

    • Users need a purchased license
    • Better after-sales, more expensive
    • Allows a limited trial

  2. Shareware

    • Unlimited trial period. Lets user decide whether to purchase at the end.
    • Copies can be freely distributed = can acquire through different ways.

  3. Freeware

    • Can install and use for free. No limits.
    • Some allows only non-commercial / personal use.
    • May prohibit distribution.

  4. Public Domain

    • Free of charge
    • No limitation on re-distribution.
    • May provide source code to users. Community can contribute and improve.

5.3 Piracy

  • Distribution = criminal offence = imprisonment + fine
  • Posession = civil offence

5.4 Prevent infringement

Four levels of CC (Creative Commons):

  • BY (Attribution) Let others distribute, copy, display... only if given credit in requested form.
  • SA (Share-alike) Let others create derivatives, under same license of the work.
  • NC (Non-Commercial) Let others copy, distribute, display... only for non-commercial purposes.
  • ND (No Derivative Works) Let others copy, distribute, display... only verbatim copies, not derivatives.

Plagiarism = copy without citing.

6 Internet Security

6.1 Cyberbullying

  • Spreading rumours by internet, to damage reputation of someone.
  • Distributing embarrasing / insulting photos / videos online.
  • Disclosing personal information (names, home address, phone number...) WITHOUT CONSENT.

Results:

  • Lose motivation in studies
  • Health problems
  • Resort to drugs...

Netiquette: Network etiquette.

  • Think before posting No personal attacks / insults when having different opinions. No abusive language / hate speech.

  • Respect privacy Do not forward / post private photos / messages without consent.

  • Legal Cyberbullies can be punished by law for crimes comitted online.

6.2 Malware

  • Computer virus Attached to EXEs and macro scripts in documents / spreadsheets. When users run the program / open the document, the virus may damage the data on the computer and infect other programs.

    May replicate itself.

  • Trojan horse Disguised as useful application, e.g., crack, jailbreak... Infiltrates the system / remotely controls / steals personal information when run. Attaches to other programs.

    They do not replicate.

  • Worm Replicates itself across computer networks.

    E.g., when opened an infected email attachment, a worm can replicate itself and seld copies to all contacts in address book.

Protective measures:

  • Anti-virus software Protects computer by scanning and isolating infected files.

    Constantly upgrade the virus signature / turn on auto-update feature.

  • Firewall Can be software / hardware. Most OS's come with firewall installed.

    Protects system agains malicious network packets, and prevents spread of worm by blocking outgoing traffic.

  • Updates Upgrade OS to the latest version regularly. Old software is prone to attacks.

6.3 Social Engineering

Manipulate people for sensitive information.

  • Baiting Exploits victim's curiosity. E.g., intentionally-dropped flash drive with malware insatlled. When victim inserts it into the computer, the malware will install automatically.

  • Pretexting Victims are told a convincing story, and persuaded to give personal information / transfer money. E.g., an email stating the child to be kidnapped, and require victim to pay ransom.

  • Phising Fake websites created with similar layouts as real banking websites, and distributed by email to fool victims.

6.4 Blackmail

Forcing someone to give benefits through threatening.

  • Webcam blackmail Use online video chats while secretly recording, and lures victims to take off clothes. Then, victim is blackmailed by recorded videos.

  • Ransomware Encrypts data on systems, and require a ransom to be paid to hacker, in order to unlock files. If not paid before a deadline, all files will be destroyed. Businesses and individuals can be victims of ransomware attack.

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