1. Week 1 LBSC 690 Information Technology
Computing
Week 1
LBSC 690
Information Technology

2. Teaching Theater Introduction
Logging on
Choosing a good password
Key directories
Shared class materials are on N:\SHARE
Your personal directory is at M:
Taking notes

3. Class Directory Pair up with a neighbor Introduce yourselves
Bring up the class directory
Work together to craft entries for both of you

4. Agenda Looking backwards What “computers” do How they do it
About the course

5. A Very Brief History of Computing
Hardware: all developed for the government
Mechanical: essentially a big adding machine
Analog: designed for calculus, limited accuracy
Digital: early machines filled a room
Microchips: designed for missile guidance
Software: initial applications were military
Numeric: computing gun angles
Symbolic: Code-breaking

6. Commercial Developments
Mainframes (1960’s)
IBM
Minicomputers(1970’s)
DEC
Personal computers (1980’s)
Apple, Microsoft
Networks (1990’s)
Web

7. Hardware Processing Cycle
Input comes from somewhere
Keyboard, mouse, microphone, camera, …
The system does something with it
Processor, memory, software, network, …
Output goes somewhere
Monitor, speaker, robot controls, …

8. Discussion Point: What’s Special About Computers?
Digital content
Perfect copies
Programmed behavior
Speed
Repetition
Complexity

9. The Big Picture
Memory
Processor
Network

10. Computer Hardware Central Processing Unit (CPU) Communications “Bus”
Intel Pentium, Motorola Power PC, …
Communications “Bus”
PCI, ISA, USB, Firewire, …
Storage devices
Cache, RAM, hard drive, floppy disk, …
External communications
Modem, LAN, …

11. Extracted From Shelly Cashman Vermatt’s Discovering Computers 2004

12. Thinking About Time Total “transfer time” is what counts
Time for first bit + time between first and last bits
For long distances, the first factor is important
California: 1/80 of a second (by optical fiber)
London:1/4 of a second (by satellite)
For large files, the second factor dominates
Number of bits per second is limited by physics
Today, we will focus on the second factor

13. Thinking About Speed Speed can be expressed two ways:
How long to do something once?
Memory speed measured as “access time”
How many things can you do in one second?
Processor speed measured in “instructions per second”
Convenient units are typically used
“10 microseconds” rather than “ seconds”
When comparing speeds, convert units first!

14. The Storage Hierarchy The problem: The solution:
Fast memory devices are expensive
So large memory devices are slow!
But fast access to large memories is needed
The solution:
Keep what you need often in small (fast) places
Keep the rest in large (slow) places
Get things to the fast place before you need them

15. System Architecture Keyboard Mouse Sound Card Video Card Input
Controller
Bus
Hard
Drive
CD/
DVD
Floppy
RAM
CPU
Cache
Motherboard

16. Everything is Relative
The CPU is the fastest part of a computer
1 GHz Pentium = 1,000 MIPS
One operation every 1 nanosecond
Cache memory is fast enough to keep up
32 kB L1 cache on chip, runs at CPU speed
512 kB L2 cache on motherboard, ~10 ns
RAM is larger, but slower
128 MB or more, ~50 ns

17. Converting Units Speed Size Unit Abbr Fraction of a sec second sec 1
millisecond ms 1/1,000
microsecond ms 1/1,000,000
nanosecond ns 1/1,000,000,000
picosecond ps 1/1,000,000,000,000
Size
Unit Abbr Bytes
bit b 1/8
byte B 1
kilobyte kB 1,024
megabyte MB 1,048,576
gigabyte GB 1,073,741,824
terabyte TB 1,099,511,627,776

18. “Solid-State” Memory ROM Cache (“Static” RAM) (“Dynamic”) RAM
Does not require power to retain the contents
Cache (“Static” RAM)
Level 1 (L1) cache is on-chip
Level 2 (L2) cache is reached over the bus
(“Dynamic”) RAM
DRAM is used only by the CPU
VRAM is shared by CPU and display driver

19. Breaks Option 1 (5:30-8:15) Option 2 (5:30-8:30)
10 minute break after the first hour
5 minute break after the second hour
Option 2 (5:30-8:30)
15 minute break after the first hour
15 minute break after the second hour
No food or drink in the teaching theater

20. System Architecture Keyboard Mouse Sound Card Video Card Input
Controller
Bus
Hard
Drive
CD/
DVD
Floppy
RAM
CPU
Cache
Mass Storage

21. “Rotating” Memory Fixed magnetic disk (“hard drive”)
May be partitioned into multiple volumes
In Windows, referred to as C:, D:, E:, …
In Unix, referred to as /software, /homes, /mail, …
Removable magnetic disk
Floppy disk, zip drives, …
Removal optical disk
CDROM, DVD, CD-R, CD-RW, DVD+RW, …

22. How Disks Work
Extracted From Shelly Cashman Vermatt’s Discovering Computers 2004

23. Trading Speed for Space
Hard disk is larger than RAM but much slower
10 ms access time and 100 GB is typical
One thousand times larger than RAM
10 million times slower than the CPU!
The initial access is the slow part
Subsequent bytes sent at 17 MB/sec (60 ns/byte)
As virtual memory, makes RAM seem larger
But things slow down beyond physical RAM

24. Discussion Point: Moore’s Law
Processing speed doubles every 18 months
Faster CPU, longer words, larger L1 cache
Cost/bit for RAM drops 50% every 12 months
Small decrease in feature size has large effect
Cost/bit for disk drops 50% every 12 months
But transfer rates don’t improve much

25. RAID Disks can fail in two ways: RAID arrays put one bit on each disk
Bad sectors (data sectors, directory sectors)
Mechanical failure
RAID arrays put one bit on each disk
~30% extra allows reconstruction if one disk fails
“Parallel” data transfer is faster than “serial”

26. How RAID Works Original Data (256 possible values)
Encoded Data (4096 possible values) …
Errors

27. Tape Backup Tapes store data sequentially
Very fast transfer, but not “random access”
Used as backup storage for fixed disks
Weekly incremental backup is a good idea
With a complete (“level zero”) monthly backup
Used for archival storage
Higher data density than DVD’s

28. Discussion Point: Migration
What format should old tapes be converted to?
Newer tape CD
DVD
How often must we “refresh” these media?
How can we afford this?

29. Types of Software Application programs (e.g., Internet Explorer)
What you normally think of as a “program”
Compilers and interpreters (e.g., JavaScript)
Allow programmers to create new behavior
Operating system (e.g., Windows XP)
Moves data between disk and RAM (+lots more!)
Embedded program (e.g., BIOS)
Permanent software inside some device

30. Installing Applications
Copy to a permanent place on your hard drive
From a CD, the Internet, …
Installs any other required programs
“DLL” files can be shared by several applications
Register the program’s location
Associates icons/start menu items with it
Configures the uninstaller for later removal
Configure it for your system
Where to find data files and other programs

31. Discussion Point: What’s a Virus?
Characteristics
Initiation
Behavior
Propagation
Spyware
Detection

32. Graphical User Interfaces
Easy way to perform simple tasks
Used to start programs, manage files, …
Relies on a physical metaphor (e.g., a desktop)
Built into most modern operating systems
Windows XP, Mac System 10, Unix X-windows
Application programs include similar ideas
Point-and-click, drag and drop, …

33. Cursor-based Interfaces
Useful for specifying complex operations
Available in most operating systems
SSH connection to WAM
Command window in Windows XP
Used when graphical display is difficult
Dial-in access from older computers

34. Summary Speed, cost, and size:
You can easily get any 2, but not all 3
Computers use cache as a compromise strategy
Hardware and software work synergistically
Our focus will be on software and the Internet
But understand hardware abilities and limitations

35. Course Goals Conceptual Practical Understand computers and networks
Appreciate the effects of design tradeoffs
Evaluate the role of information technology
Practical
Learn to use some common software tools
Solve a practical problem
Develop a personal plan for further study

36. Some Motivating Questions
What are the technical limitations on:
Privacy?
Copyright?
How will digital libraries develop?
What capabilities will they have?
How will they interact with distance education?
How might electronic publishing impact:
Access to research results?
Research quality?

37. Some IT Courses at CLIS 708D Digital Library Implementation
708F Digital Library Technology and Policy
708V IR and Info Analysis on the Internet
790 Building the Human-Computer Interface
733 Seminar in Networks
793 Database Design
796 Information Retrieval Systems

38. Instructional Staff Professor: Dr. Doug Oard
Offices: HBK 4121G/AVW 4173
(finds me anywhere)
Teaching Assistant: Neetu Ahuja
Labs Thu/Sat/Sun in HBK 2101
Teaching Theater Technician

39. Approach Readings Class sessions Homework, lab sessions, project
Provide background and detail
Class sessions
Provide conceptual structure
Outline notes provided in class
Slides and videotapes available
Homework, lab sessions, project
Provide hands-on experience
Quiz, exams
Measure progress

40. A Personal Approach to Learning
Work ahead, so that you are never behind
Ask questions about the readings
Augment practical skills with OIT training
Pick topics you want to learn more about
Start thinking about your project soon
Pick partners with complementary skills

41. Getting From Here to There
What you need to know
Quiz
Midterm
What I did in Grad School
Nobody does this!
What you know now

42. Syllabus Master the tools in the first 7 weeks
2 readings and one homework each week
Explore integrating issues the last 7 weeks
1 reading each week + the project

43. Grading 35-38% individual work
Exams: 25% for the best, 10% for the other
12-15% group work, in any groups you like
3% each for best 5 of the 7 homework/quiz
40% group work, in 3-person project teams
25% for the project, 15% for the report
10% class participation

44. Some Observations on Grading
One exam is worth more than all the homework
Message: Use the homework to learn the material
Midterm grades predict final grades well
Message: Develop sound study skills early
You need not be good at everything to get an A
But you do need to be excellent at several things

45. The Fine Print Group work is encouraged on homework
But you must personally write what you turn in
Deadlines are firm and sharp
Allowances for individual circumstances are included in the grading computation
Academic integrity is a serious matter
No group work during the exams or the quiz!
Don’t discuss exam until all sections are done

46. Course Materials Textbook Supplemental readings
Daily access to a networked computer!
A few floppy disks or a USB memory stick

47. Computing at Maryland Open Labs (IBM, Mac, Unix)
HBK 2101 (open lab), HBK 2108 (CLIS only)
PG2 and HBK Basement: 24 hr WAM labs
Need an aITs “pay for print” account
Dial-in access (Unix only)
College Park (301) (3hr)/ (15min)
Baltimore (410) (3hr)/ (15min)
WAM userid and password required

48. Homework Goals Think about relative speed and relative size
Interpret specifications for computer systems
Try some “back of the envelope” calculations
Some helpful hints:
There is a calculator in Windows XP accessories
If you’re rusty on math, the TA can help in lab

49. Saving Your Notes First, save the Word file on your M: drive
You can use see in the CLIS computer lab
Use the “ttconnect” program to mount your files
If you have a floppy or a USB memory stick
Save the Word file again there
You can also transfer the file by FTP
From home, connect to ttclass.umd.edu

50. Obtaining Recordings All classes recorded Available over the Internet
Fixed camera angle, generally focused on screen
Microphones in the ceiling
Available over the Internet
Postage-stamp video, some audio distortion
Videotapes available in Wasserman Library
Available for viewing only in the library

51. Before You Go
On a sheet of paper, answer the following (ungraded) question (no names, please):
What was the muddiest point in today’s class?