computers and society ist 2710 section 006 class #5: 2/6/08

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


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.


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).


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



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)


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


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.


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


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


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


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)


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


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


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


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


Protection

• VPN uses encryptiono Virtual Private Network

• Wireless can be insecure if owner is not careful


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


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


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!



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 …



• 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


• 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
