Computing
Week 1
LBSC 690
Information Technology
![](3D"slide0001_image001.jpg")
Teaching Theater Introduction
&#=
8226;Logging
on
&=
#8211;Userid
and password are your university account
&#=
8226;Key
directories
&=
#8211;Shared
class materials are on N:\SHARE
&=
#8211;Your
personal directory is at M:
&#=
8226;Taking
notes
Agenda
&#=
8226;Looking
backwards
&#=
8226;What
“computers” do
&#=
8226;How
they do it
&#=
8226;About
the course
Goals
&#=
8226;By
the end of this class, you will…
&#=
8211;Have
a basic understanding of computers
&=
#8211;Know
how to think about “space,”
“time”
and “=
speed”
–Understand
of how computers store data and move data around
A Very
Brief History of Computing
&#=
8226;Hardware:
all developed for the government
&=
#8211;Mechanical:
essentially a big adding machine
&=
#8211;Analog:
designed for calculus, limited accuracy
&=
#8211;Digital:
early machines filled a room
&#=
8211;Microchips:
designed for missile guidance
&#=
8226;Software:
initial applications were military
&=
#8211;Numeric:
computing gun angles
&=
#8211;Symbolic:
code-breaking
Commercial Developments
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&#=
8226;Mainframes
(1960’s)
&=
#8211;IBM
&#=
8226;Minicomputers(1970’s)
&=
#8211;DEC
&#=
8226;Personal
computers (1980’s)
&=
#8211;Apple,
Microsoft
&#=
8226;Networks
(1990’s)
&=
#8211;Web
&#=
8226;Convergence
(2000’s)
&=
#8211;Cell
phones/PDA, TV/Computer, …
Hardware Processing Cycle<=
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&#=
8226;Input
comes from somewhere
&=
#8211;Keyboard,
mouse, microphone, camera, …
&#=
8226;The
system does something with it
&=
#8211;Processor,
memory, software, network, …
&#=
8226;Output
goes somewhere
&=
#8211;Monitor,
speaker, robot controls, …
Discussion Point:
What’s Special About Comput= ers?
What’s Special About Comput= ers?
&#=
8226;Digital
content
&=
#8211;Perfect
copies
&#=
8226;Programmed
behavior
&=
#8211;Speed
&=
#8211;Repetition
&=
#8211;Complexity
![](3D"slide0006_image002.gif")
The Big Picture
Processor
Memory
![](3D"slide0006_image007.gif")
![](3D"slide0006_image010.gif")
Network
![](3D"slide0006_image012.gif")
Computer Hardware
&#=
8226;Central
Processing Unit (CPU)
&=
#8211;Intel
Xeon, Motorola Power PC, …
&#=
8226;Communications
“Bus”
&=
#8211;FSB,
PCI, ISA, USB, Firewire, …
&#=
8226;Storage
devices
&=
#8211;Cache,
RAM, hard drive, floppy disk, …
&#=
8226;External
communications
&=
#8211;Modem,
Ethernet, GPRS, 802.11, …
![](3D"slide0065_image013.gif")
Extracted From Shelly Cashman Vermatt’s Discovering
Computers 2004
Thinking About Transfer Time
&#=
8226;Total
“transfer time” is what counts
&#=
8211;Time
for first bit + time between first and last bits
&#=
8226;For
long distances, first bit time is important
&=
#8211;California:
1/80 of a second (by optical fiber)
&=
#8211;London:1/4
of a second (by satellite)
&#=
8226;For
large files, bits per second dominates
&=
#8211;Number
of bits per second is limited by physics
&#=
8226;Inside
computers, bits per second dominates
Some Definitions
•Latency:=
the amount of time it takes data to travel from source to
destination
•Bandwidth:
the amount of data that can be transmitted in a
fixed amount of time
Discussion Point
=
226;What
are the latency and bandwidth requirements for the following
applications:
&=
#8211;Streaming
audio (e.g., NPR broadcast over Web)
&=
#8211;Streaming
video (e.g., CNN broadcast over Web)
&=
#8211;Audio
chat
&=
#8211;Video
conferencing
Thinking About Speed
&#=
8226;Speed
can be expressed two ways:
&=
#8211;How
long to do something once?
&=
#8226;Memory
speed measured as “access
time”=
&=
#8211;How
many things can you do in one second?
&=
#8226;Processor
speed measured in “instructions
per second&=
#8221;
&#=
8226;Convenient
units are typically used
&#=
8211;“10
microseconds”
rather than “0.00001
secondsR=
21;
&#=
8226;When
comparing speeds, convert units first!
The Storage Hierarchy
&#=
8226;The
problem:
&#=
8211;Fast
memory is expensive
&=
#8226;So
large memory is slow!
&=
#8211;But
fast access to large memories is needed
&#=
8226;The
solution:
&=
#8211;Keep
what you need often in small (fast) places
&=
#8226;Keep
the rest in large (slow) places
&=
#8211;Get
things to the fast place before you need them
Best of Both Worlds?
![](3D"slide0091_image015.gif")
![](3D"slide0091_image017.gif")
+
=3D
![](3D"slide0091_image018.gif")
Small, but fast…
Large, but slow…
Large =
and fast?!
Thi=
nk
about your bookshelf and the library…
![](3D"slide0064_image019.gif")
System Architecture
CPU
RAM
Hard
Drive
CD/
DVD
Cache
![](3D"slide0064_image020.gif")
![](3D"slide0064_image021.gif")
![](3D"slide0064_image022.gif")
![](3D"slide0064_image023.gif")
![](3D"slide0064_image024.gif")
![](3D"slide0064_image025.gif")
Motherboard
System Bus
Video
Card
Input
Controller
Keyboard
Mouse
Sound
Card
USB Port
L1
L2
Front Side Bus
Everything is Relative
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&#=
8226;The
CPU is the fastest part of a computer
&#=
8211;3
GHz Core 2 Duo =3D 6,000 MIPS
&=
#8226;3
operations per processor every nanosecond
&#=
8226;Cache
memory is fast enough to keep up
&=
#8211;128
kB L1 cache on chip (dedicated, CPU speed)
&#=
8211;4
MB L2 cache on chip (shared, CPU speed)
&#=
8226;RAM
is larger, but slower
&#=
8211;1
GB or more, ~6 ns
![](3D"slide0081_image026.gif")
Units of Time
10-15<=
span
style=3D'font-family:"Times New Roman";mso-ascii-font-family:"Times New Ro=
man";
font-size:86%'> =3D
1/1,000,000,000,000,000
fs
femtosecond<=
/div>
10-12<=
span
style=3D'font-family:"Times New Roman";mso-ascii-font-family:"Times New Ro=
man";
font-size:86%'> =3D
1/1,000,000,000,000
ps
picosecond
10-9 =3D 1/1,000,0=
00,000
ns
nanosecond
10-6 =3D 1/1,000,0=
00
ms=
microsecond<=
/div>
10-3 =3D 1/1,000
ms
millisecond<=
/div>
1
sec/s
second
Duration (second=
s)
Abbreviation=
Unit<=
/div>
![](3D"slide0082_image027.gif")
Units of Frequency
109 =3D 1,000,000=
,000
GHz
gigahertz
106 =3D 1,000,000=
MHz
megahertz
103 =3D 1,000
KHz
kilohertz
1
Hz
hertz
Cycles per secon=
d
Abbreviation=
Unit<=
/div>
![](3D"slide0077_image028.gif")
Units of Size
petabyte
terabyte
gigabyte
megabyte
kilobyte
byte
bit
Unit<=
/div>
PB
TB
GB
MB
KB
B
b
Abbreviation=
250 =3D
1,125,899,906,842,624
240 =3D 1,099,511=
,627,776
230 =3D 1,073,741=
,824
220 =3D 1,048,576=
210 =3D 1024
1
1/8
Size (bytes)=
![](3D"slide0093_image029.gif")
The Storage Hierarchy
Very cheap
100 GB
~10 ms
Hard drive
Cheap
1 GB
~10 ns
RAM
Expensive
4 MB
~1 ns
Cache
Very expensive
256 B
~300 ps
Registers
Cost
Size
Speed
Type
Locality
•Spatial
locality: If the system fetched x=
,
it is likely to fetch data located n=
ear x
•
•Temporal
locality: If the system fetched x=
,
it is likely to fetch x
again
•
•Insight behind =
the
storage hierarchy:
–Move important =
data
from slow, large memory to fast, small
memory
“Solid-State”
Memory
&#=
8226;ROM
&=
#8211;Does
not require power to retain content
&=
#8211;Used
for “Basic Input/Output System” (BIOS)
&#=
8226;Cache
(Fast low-power “Static” RAM)
&=
#8211;Level
1 (L1) cache: small, single-purpose
&=
#8211;Level
2 (L2) cache: larger, shared
&#=
8226;(“Dynamic”)
RAM (Slower, power hungry)
&=
#8211;Reached
over the “Front-Side Bus” (FSB)
&#=
8226;Flash
memory (fast read, slow write EEPROM)
&=
#8211;Reached
over USB bus or SD socket
&=
#8211;Used
in memory sticks (“non-volatile” storage)
Breaks
&#=
8226;Typically,
two breaks
&=
#8211;10
minute break after the first hour
&=
#8211;5
minute break after the second hour
&#=
8226;No
food or drink in the teaching theater
Introductions
&#=
8226;Over
break:
&=
#8211;Pair
up with one person you don’t yet know
&=
#8211;Introduce
yourselves to each other
&#=
8226;After
break:
&=
#8211;Introduce
your partner to us in 30 seconds
&=
#8211;Name,
background, goals, one interesting thing
![](3D"slide0069_image030.gif")
System Architecture
CPU
RAM
Hard
Drive
CD/
DVD
Cache
![](3D"slide0069_image031.gif")
![](3D"slide0069_image032.gif")
![](3D"slide0069_image033.gif")
![](3D"slide0069_image034.gif")
![](3D"slide0069_image035.gif")
![](3D"slide0069_image036.gif")
Motherboard
System Bus
Video
Card
Input
Controller
Keyboard
Mouse
Sound
Card
USB Port
L1
L2
Front Side Bus
“Rotating”
Memory
&#=
8226;Fixed
magnetic disk (“hard drive”)
&=
#8211;May
be partitioned into multiple volumes
&=
#8226;In
Windows, referred to as C:, D:, E:, …
&=
#8226;In
Unix, referred to as /software, /homes, /mail, …
&#=
8226;Removable
magnetic disk
&#=
8211;Floppy
disk, zip drives, …
&#=
8226;Removal
optical disk
&=
#8211;CDROM,
DVD, CD-R, CD-RW, DVD+RW, …
How Disks Work
![](3D"slide0066_image038.gif")
![](3D"slide0066_image040.gif")
Extracted From Shelly Cashman Vermatt’s Discovering
Computers 2004
Trading Speed for Space
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&#=
8226;Hard
disk is larger than RAM but much
slower
&=
#8211;typical:
10 ms access time, 100 GB (at 5400 rpm)
&=
#8226;One
thousand times larger than RAM
&=
#8226;10
million times slower than the CPU!
&#=
8226;The
initial access is the slow part
&=
#8211;Subsequent
bytes sent at 17 MB/sec (60 ns/byte)
=
226;As
“virtual memory,” makes RAM seem
larger
&=
#8211;But
too little physical RAM results in “thrashing”
Everything is Relative
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&#=
8226;The
CPU is the fastest part of a computer
&#=
8211;3
GHz Core 2 Duo =3D 6,000 MIPS
&=
#8226;3
operations per processor every nanosecond
&#=
8226;Cache
memory is fast enough to keep up
&=
#8211;128
kB L1 cache on chip (dedicated, CPU speed)
&#=
8211;4
MB L2 cache on chip (shared, CPU speed)
&#=
8226;RAM
is larger, but slower
&#=
8211;1
GB or more, ~6 ns
Discussion Point: Moore’s L=
aw
&#=
8226;Processing
speed doubles every 18 months
&=
#8211;Faster
CPU, longer words, larger L1 cache
&#=
8226;Cost/bit
for RAM drops 50% every 12 months
&=
#8211;Small
decrease in feature size has large effect
&#=
8226;Cost/bit
for disk drops 50% every 12 months
&=
#8211;But
transfer rates don’t improve much
![](3D"slide0087_image042.jpg")
Team Exercise
&#=
8226;Form
into groups of 4
–Be
sure you have someone who has used Excel before
in your group
=
226;Answer
question 1(d) from the Fall 1996 final exam
(available on the course Web site)
RAID-5
&#=
8226;Disks
can fail in two ways:
&=
#8211;Bad
sectors (data sectors, directory sectors)
&=
#8211;Mechanical
failure
&#=
8226;RAID-5
arrays “stripe” blocks across disks
&=
#8211;~30%
“parity” allows reconstruction if one disk fails
&#=
8226;“Parallel”
data transfer is faster than “serial”
&=
#8211;“RAID-0” uses
striping for speed, but without parity
![](3D"slide0057_image043.gif")
=
…
=
000011110000
000010110000
000010010000
=
000010000000
=
…
How Parity Works
![](3D"slide0057_image044.gif")
![](3D"slide0057_image045.gif")
Original Data (256 possible values)
![](3D"slide0057_image046.gif")
Tape Backup
&#=
8226;Tapes
store data sequentially
&=
#8211;Very
fast transfer, but not “random
access̶=
1;
&#=
8226;Used
as backup storage for fixed disks
&#=
8211;Weekly
incremental backup is a good idea
&=
#8226;With
a complete (“level zero”) monthly backup
&#=
8226;Used
for archival storage
&=
#8211;Higher
data density than DVD’s
Discussion Point: Migration
&#=
8226;What
format should old tapes be converted to?
&=
#8211;Newer
tape
&=
#8211;CD
&=
#8211;DVD
&#=
8226;How
often must we “refresh” these media?
&#=
8226;How
can we afford this?
Types of Software
&#=
8226;Application
programs (e.g., Internet Explorer)
&=
#8211;What
you normally think of as a “program”
&#=
8226;Compilers
and interpreters (e.g., JavaScript)
&#=
8211;Allow
programmers to create new behavior
&#=
8226;Operating
system (e.g., Windows Vista)
&=
#8211;Moves
data between disk and RAM (+lots more!)
&#=
8226;Embedded
program (e.g., BIOS)
&=
#8211;Permanent
software inside some device
Installing Applications
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=
226;Copy
to a permanent place on your hard drive
&#=
8211;From
a CD, the Internet, …
&#=
8226;Installs
any other required programs
&=
#8211;“DLL” files =
can be
shared by several applications
&#=
8226;Register
the program’s location
&#=
8211;Associates
icons/start menu items with it
&=
#8211;Configures
the uninstaller for later removal
&#=
8226;Configure
it for your system
&=
#8211;Where
to find data files and other programs
Discussion Point: What’s a
Virus?
&#=
8226;Characteristics
&=
#8211;Initiation
&=
#8211;Behavior
&=
#8211;Propagation
&#=
8226;Spyware
&#=
8226;Detection
Graphical User Interfaces<=
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&#=
8226;Easy
way to perform simple tasks
&=
#8211;Used
to start programs, manage files, …
&=
#8211;Relies
on a physical metaphor (e.g., a desktop)
&#=
8226;Built
into most modern operating systems
&=
#8211;Windows
XP, Mac OS-X, Unix X-windows
&#=
8226;Application
programs include similar ideas
&=
#8211;Point-and-click,
drag and drop, …
Cursor-based Interfaces
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&#=
8226;Useful
for specifying complex operations
&=
#8211;Or
when graphical display is impractical
&#=
8226;Available
in most operating systems
&=
#8211;SSH
connection to WAM
&=
#8211;Command
window in Windows XP
Summary
&#=
8226;Speed,
cost, and size:
&#=
8211;You
can easily get any 2, but not all 3
&=
#8211;Computers
use caching as a compromise strategy
&#=
8226;Hardware
and software work synergistically
&=
#8211;Our
focus will be on software and the Internet
&=
#8211;But
understand hardware abilities and limitations
Course Goals
&#=
8226;Conceptual
&=
#8211;Understand
computers and networks
&=
#8211;Appreciate
the effects of design tradeoffs
&=
#8211;Evaluate
the role of information technology
&#=
8226;Practical
&=
#8211;Learn
to use some common tools
&=
#8211;Solve
a practical problem
&=
#8211;Develop
a personal plan for further study
Some Motivating Questions<=
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&#=
8226;What
are the technical implications for:
&=
#8211;Privacy?
&=
#8211;Copyright?
&#=
8226;How
will digital repositories develop?
&=
#8211;How
will they interact with distance education?
&=
#8211;What
are the implications for archives?
&#=
8226;How
might electronic dissemination impact:
&=
#8211;Roles
of authors, publishers, and readers?
&=
#8211;Access
by disenfranchised populations?
Some LBSC Courses on IT
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•708E E-Government
•708Q Digital Preservation
•708T Transformational Technologie=
s
•715 Knowledge Management
•733 Networks
=
•790 Building User Interfaces
(programming)
•793 Database Design
=
•795 Human-Computer Interaction&#=
13;
•796 Information Retrieval System=
s
Instructional Staff
&#=
8226;Professor:
Dr. Doug Oard
&=
#8211;Offices:
HBK 4121G/AVW 3145
&=
#8211;Email:
oard@umd.edu
(finds me anywhere)
&#=
8226;Teaching
Assistant: Rebekah Fairbank
&=
#8211;Office:
HBK 4120
&=
#8211;Lab
time+location TBA
&=
#8211;Email:
rlf45 (at) umd.edu
&#=
8226;Teaching
Theater Technician
Approach
&#=
8226;Readings
&=
#8211;Provide
background and detail
&#=
8226;Class
sessions
&=
#8211;Provide
conceptual structure
&=
#8226;Outline
notes provided in class
&=
#8226;Slides
and videotapes available
&#=
8226;Homework,
lab sessions, project
&=
#8211;Provide
hands-on experience
&#=
8226;Quiz,
exams
&=
#8211;Measure
progress
The Grand Plan
![](3D"slide0067_image047.gif")
Networking
HTML/XML
Multimedia
Computers
![](3D"slide0067_image048.gif")
HCI
Search
CMC
Web
Life Cycle
Policy
![](3D"slide0067_image049.gif")
Databases
Programming
Web Databases
![](3D"slide0067_image050.gif")
Midterm
![](3D"slide0067_image051.gif")
Project
Final
![](3D"slide0067_image052.gif")
Quiz
A Personal Approach to Learning
=
226;Work
ahead, so that you are never
behind
&#=
8226;Ask
questions about the readings
&#=
8226;Augment
practical skills with outside resources
&#=
8226;Pick
topics you want to learn more about
&#=
8226;Start
thinking about your project soon
&=
#8211;Pick
partners with complementary skills<=
/span>
Getting From Here to There=
![](3D"slide0050_image053.gif")
![](3D"slide0050_image054.gif")
![](3D"slide0050_image055.gif")
![](3D"slide0050_image056.gif")
What you know now
What you need to know
![](3D"slide0050_image057.gif")
Midterm
![](3D"slide0050_image058.gif")
![3D"Text](3D"slide0050_image059.gif")
Nobody does this!
![](3D"dsld0050_image060.gif")
Syllabus
&#=
8226;Master
the tools in the first 7 weeks
&#=
8211;2
readings and one homework most weeks
&#=
8226;Explore
integrating issues the last 7 weeks
&=
#8211;1
reading each week + the project
Grading
&#=
8226;35-38%
individual work
&=
#8211;Exams:
25% for the best, 10% for the other
=
226;12-15%
group work, in any groups you like
&=
#8211;3%
each for best 5 of the 7 homework/quiz
&#=
8226;40%
group work, in 3-person project teams
&=
#8211;30%
for the project, 10% for presentation+report
&#=
8226;10%
“class” participation
Some Observations on Grading
&#=
8226;One
exam is worth more than all the homework
&=
#8211;Message: Use the homework to learn the
material
&#=
8226;Midterm
grades predict final grades well
&=
#8211;Message:
Develop sound study skills early
&#=
8226;You
need not be good at everything to get an A
&=
#8211;But
you do need to be excellent
at several things
The Fine Print
&#=
8226;Group
work is encouraged on homework
&=
#8211;But
you must personally write what you turn in
&#=
8226;Deadlines
are firm and sharp
–Allowances
for individual circumstances are included in the grading
computation
=
226;Academic
integrity is a serious matter
&=
#8211;No
group work during the exams or the quiz!
&=
#8211;Don’t
discuss exam until all sections are done
Course Materials
Computing at Maryland
&#=
8226;Computer
Labs (IBM, Mac)
&=
#8211;PG2: 24 hr WAM lab
<=
/div>
&=
#8226;Need
an OIT “LPCR” ac=
count
for printing
&#=
8226;Dial-in
access (Unix only)
–Sailor:
http://www.sailor.lib.md.us/help/=
ppp/index.html
Homework Goals
&#=
8226;Think
about relative speed and relative size
&#=
8226;Interpret
specifications for computer systems
&#=
8226;Try
some “back of the envelope” calculations
&#=
8226;Some
helpful hints:
&=
#8211;There
is a calculator in Windows accessories
&=
#8211;If
you’re rusty on math, the TA can help in lab
Saving Your Notes
&#=
8226;First,
save the Word file on your M: drive
&=
#8211;Connect
over the Web to pick it up
&=
#8226;http://ttclass.umd.edu
Obtaining Recordings
&#=
8226;All
classes recorded
&=
#8211;Fixed
camera angle with screen in field of view
&#=
8211;Microphones
in the ceiling
&#=
8226;Usually
available over the Internet
&=
#8211;Postage-stamp
video, some audio distortion
&#=
8211;Useful
for seeing what slide we were on
&#=
8226;Videotapes
available outside my office
&#=
8211;Please
don’t take for more than 24 hours
Before You Go
• On a sheet of paper, answer the following (ungraded)
question (no names, please):
=
What
was the muddiest point in today’s clas=
s?
Click to edit Master text styles
Second level
Third level
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Fifth level
' + ENDSHOW_MESG + '
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