Computers and Society
IST 2710
Section 006
Class #5: 2/6/08
http://www.is.wayne.edu/drbowen/casw08
Quiz Results
• Average is about 73, but some people did
very badly
o Two blank diskettes – CHECK!
o Many questions left blank – NEVER DO THIS!
• Question 2 was worst
o 2A (2 types of storage) average 50
o 2B (6 stypes of computers) average 46
o 2C (data and information) average 60
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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.
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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).
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Turning in Work
• Do not staple all of your work together
o If I cannot separate it easily, I will turn it back
for you to separate
• Turn each assignment in separately
o Each lab
o Each homework assignment
o Each assignment should be stapled
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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
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Storing Pictures in a Computer
• Graphics:
o Screen divided into
“pixels”
o Seeing “jaggies” – aliasing
o Smoothing edge – anti-aliasing
• Computer stores a color code for each
pixel
o Color code is RGB (amount of Red, Green,
Blue)
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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
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Color Codes
• Many different codes – some examples:
o 16-Bit color (“High Color”): 6-5-5. 65000+
colors, not bad
o 24-Bit or 3 Byte color (“True Color): one byte
each for Red, Green, Blue
o Good-quality color photo
o 32-Bit color. Some printers offering this.
Screen cannot register more than 3, but
printer can be higher resolution.
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Storing Graphics
• Bytes per graphic – product of:
o Number of pixels (number high times number
wide)
o Color depth – bytes per pixel
o 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
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Storing Data
• How many different values (or codes) can
be stored in a given number of bits
• Do on board
• Work out
o Lowest value
o Highest value
o Number of different values
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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
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Chapter 4 – Computer Security
• Why be worried? They ARE after you!
o “Exploit” – bragging rights about skills
o Getting even
o Profit – sell the use of your computer
• Zombie networks, advertized on Internet
• Physical security
• Protecting against unauthorized use
o UserID (public) and Password (secret)
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Security
• Hacking – breaking into a computer
• Malware – harmful software
o Virus – corrupt files, infects others
o Worm – runs many copies, slows computer,
infects others
o Trojan horse – disguised as something useful
o Denial of Service – tie up a server with
requests
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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 – scrambling
o Public key/private key – authenticates also
Page 133 Figure 4-12
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More Protection: DB
• Strong password:
o 6 to 8 characters
o Not the same password everywhere
o Not a dictionary work, or one backwards
o Not the name of you, relative, pet, or one
backwards
o Use upper and lowercase
o Use characters, numbers and special
characters
o Compound passwords – two types
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More Protection - DB
• A good antivirus program
o Update data file AND scan engine
• Internet Security Suite
o Firewall + Antivirus, work together
o Plus other features, such as alerting user if
SSN or Credit Card Number leaves computer
• Total Security Suite
o Security Suite + disk health + backup
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Protection
• VPN uses encryption
o Virtual Private Network
• Wireless can be insecure if owner is not
careful
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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
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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 up
o USB drive and backup software
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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 place
o Editing a folder or file name
o Searching – if it is not on your diskette, it is
probably in My Documents
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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!
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Using Calculator for 2n
•
•
•
•
Start Windows Calculator
Scientific View
Dec clicked
Click these keys:
1. 2
2. x^y
3. n
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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 …
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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 …
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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
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