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Computers and SocietyIST 2710
Section 006
Class #5: 2/6/08
http://www.is.wayne.edu/drbowen/casw08
2/6/08 Computers and Society, Class 5 2
Quiz Results
• Average is about 73, but some people did very badlyo Two blank diskettes – CHECK!o Many questions left blank – NEVER DO THIS!
• Question 2 was worsto 2A (2 types of storage) average 50o 2B (6 stypes of computers) average 46o 2C (data and information) average 60
2/6/08 Computers and Society, Class 5 3
Quiz 1 Makeup
• Next week, Wednesday 2/13, 5 – 6 PM in the regular classroom.o It will be different questions, from the same
list. Some questions may, by chance, be repeated.
• If you missed the original Quiz, this is your chance to make it up.
• If you took the original Quiz but want to retake it, let me know by email.
2/6/08 Computers and Society, Class 5 4
Staying for Lab
• Two or more labs or assignments behind, must stay during Lab to get 100% attendance credit tonight - 3 labs in, and 2 assignments in. Who must stay:o EVERYONE! (Unless you have turned more
in tonight).
2/6/08 Computers and Society, Class 5 5
Turning in Work
• Do not staple all of your work togethero If I cannot separate it easily, I will turn it back
for you to separate
• Turn each assignment in separatelyo Each labo Each homework assignmento Each assignment should be stapled
University closing info
All of these:• Wayne State University Newsline :
313-577-1498• Wayne State University main website:
www.wayne.edu• Pipeline• Or sign up for email, text or cell call
o computing.wayne.edu > services > About WSU Broadcast Messaging
2/6/08 Computers and Society, Class 5 6
2/6/08 Computers and Society, Class 5 7
Storing Pictures in a Computer
• Graphics:o Screen divided into
“pixels”o Seeing “jaggies” – aliasingo Smoothing edge – anti-aliasing
• Computer stores a color code for each pixelo Color code is RGB (amount of Red, Green,
Blue)
2/6/08 Computers and Society, Class 5 8
Color Codes
• Many different codes – some examples:o Black and White, code is (usually) 1 bit for
each pixel – 0 is black, 1 white.o Greyscale: One byte per pixel (zero to 255)
• 0 is black, 255 is white, low numbers are dark shades, high numbers are bright shades
• High-quality “black and white” photo
o One-byte color: 3 bits for red (0 to 7), 2 bits for green (0 to 3), 2 bits for blue
• Big jumps in colors, can get “banding” effect
2/6/08 Computers and Society, Class 5 9
Color Codes
• Many different codes – some examples:o 16-Bit color (“High Color”): 6-5-5. 65000+
colors, not bado 24-Bit or 3 Byte color (“True Color): one byte
each for Red, Green, Blueo Good-quality color photoo 32-Bit color. Some printers offering this.
Screen cannot register more than 3, but printer can be higher resolution.
2/6/08 Computers and Society, Class 5 10
Storing Graphics• Bytes per graphic – product of:
o Number of pixels (number high times number wide)
o Color depth – bytes per pixelo Divide by: Compression factor
• Bytes = pixels high × pixels wide × bytes per pixel / compression factor
• Example: How many bytes are required to store a graphic that is 80 pixels high by 60 pixels wide, with 2 Bytes per pixel and a compression factor of 5?
• David, change the homework
2/6/08 Computers and Society, Class 5 11
Storing Data
• How many different values (or codes) can be stored in a given number of bits
• Do on board
• Work outo Lowest valueo Highest valueo Number of different values
2/6/08 Computers and Society, Class 5 12
Storing Data• Work out
o Number of different values: 2n
o Lowest value: always 0 (zero)o Highest value: 2n – 1
• Example:o How many different values can be stored in 5
bits:• 25 = 32 different values• Lowest value = 0• Highest value = 25 – 1 = 32 – 1 = 31
2/6/08 Computers and Society, Class 5 13
Chapter 4 – Computer Security
• Why be worried? They ARE after you!o “Exploit” – bragging rights about skillso Getting eveno Profit – sell the use of your computer
• Zombie networks, advertized on Internet
• Physical security
• Protecting against unauthorized useo UserID (public) and Password (secret)
2/6/08 Computers and Society, Class 5 14
Security
• Hacking – breaking into a computer
• Malware – harmful softwareo Virus – corrupt files, infects otherso Worm – runs many copies, slows computer,
infects otherso Trojan horse – disguised as something usefulo Denial of Service – tie up a server with
requests
2/6/08 Computers and Society, Class 5 15
Protection• Possessed Knowledge Access – e.g.,
password
• Possessed Object Access – e.g., card
• Biometric Access – physical characteristic
• Firewall – protects info in and out
• Anti-virus – find and destroy viruses
• Encryption – scramblingo Public key/private key – authenticates also
Page 133 Figure 4-12
2/6/08 Computers and Society, Class 5 16
More Protection: DB
• Strong password:o 6 to 8 characterso Not the same password everywhereo Not a dictionary work, or one backwardso Not the name of you, relative, pet, or one
backwardso Use upper and lowercaseo Use characters, numbers and special
characterso Compound passwords – two types
2/6/08 Computers and Society, Class 5 17
More Protection - DB
• A good antivirus programo Update data file AND scan engine
• Internet Security Suiteo Firewall + Antivirus, work togethero Plus other features, such as alerting user if
SSN or Credit Card Number leaves computer
• Total Security Suiteo Security Suite + disk health + backup
2/6/08 Computers and Society, Class 5 18
Protection
• VPN uses encryptiono Virtual Private Network
• Wireless can be insecure if owner is not careful
2/6/08 Computers and Society, Class 5 19
Online Problems
• Theft of data, etc.o Identity theft – put together enough info about
you to act as you online• Careful with SSN, mother’s maiden name
o Scams• Nigerian email• If it seems to good to be true, it probably is
o Phishing• Getting you to fill out private information
2/6/08 Computers and Society, Class 5 20
Online Protection
• Be careful giving out information – why do they need it?o Give last four digits of Social Security Number
• Digital signatures and certificates
• Backing upo USB drive and backup software
2/6/08 Computers and Society, Class 5 21
Using Windows Explorer
• Get and start a laptop
• Getting it right in the first place
• Check diskette
• Fixing things – NEVER START OVER!o Drag a folder to the right placeo Editing a folder or file nameo Searching – if it is not on your diskette, it is
probably in My Documents
Seeing File Extensions
• Windows Explorer
• Tools > File Extensions
• Hide extensions for known file types
• This also changes whether or not you see file extension in all applications!
2/6/08 Computers and Society, Class 5 22
2/6/08 Computers and Society, Class 5 23
Using Calculator for 2n
• Start Windows Calculator
• Scientific View
• Dec clicked
• Click these keys:1. 2
2. x^y
3. n
Getting Lab Startup Files #1
• Added 2/7/08
• Go to the website for all of IST 2710 (different than website just for this section)o Two ways to do this, use either one:
• Go to www.is.wayne.edu/gst2710 (notice g, not i)OR
• Go to class website at www.is.wayne.edu/drbowen/casw08
• Scroll down and right-click on the file you need, then …
2/6/08 Computers and Society, Class 5 24
Getting Lab Startup Files #2
• Scroll down and right-click on the file you need, then …
• On the shortcut menu click on “Save Target As…” (Internet Explorer) or “Save Link As… (Firefox) or the link that is most like either of these
• Save the file to your floppy diskette
• Close Browser – you’re done with it
• More on next slide …2/6/08 Computers and Society, Class 5 25
Getting Lab Startup Files #3
• You can now start the Tutorial
• When opening the file, do not use the location (folders) in the Tutorial, but instead use the location (path) that you save the file to.
• Similarly, when saving that or a changed file, save to that same location
• These directions are also on the Lab 5 sheet distributed in class
2/6/08 Computers and Society, Class 5 26