Computing
Week 1
LBSC 690
Information Technology
Teaching Theater Introduction
•	Logging on
–	Userid and password are your university account

•	Key directories
–	Shared class materials are on N:\SHARE 
–	Your personal directory is at M: 

•	Taking notes
Agenda
•	Looking backwards

•	What “computers” do

•	How they do it

•	About the course
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
Commercial Developments
•	Mainframes (1960’s)
–	IBM
•	Minicomputers(1970’s)
–	DEC
•	Personal computers (1980’s)
–	Apple, Microsoft
•	Networks (1990’s)
–	Web
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, …
Discussion Point: 
What’s Special About Computers?
•	Digital content
–	Perfect copies

•	Programmed behavior
–	Speed
–	Repetition
–	Complexity
The Big Picture
Computer Hardware
•	Central Processing Unit (CPU)
–	Intel Pentium, Motorola Power PC, …
•	Communications “Bus”
–	PCI, ISA, USB, Firewire, …
•	Storage devices
–	Cache, RAM, hard drive, floppy disk, …
•	External communications
–	Modem, LAN, …

Thinking About Transfer Time
•	Total “transfer time” is what counts
–	Time for first bit + time between first and last bits
•	For long distances, first bit time is important
–	California: 1/80 of a second (by optical fiber)
–	London:1/4 of a second (by satellite)
•	For large files, bits per second dominates
–	Number of bits per second is limited by physics
•	Inside computers, we focus on the second factor
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 “0.00001 seconds”
•	When comparing speeds, convert units first! 
The Storage Hierarchy
•	The problem:
–	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
System Architecture
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
–	128 kB L1 cache on chip, runs at CPU speed
–	1 MB L2 cache on motherboard, ~10 ns
•	RAM is larger, but slower
–	256 MB or more, ~50 ns
Converting Units
Speed

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
“Solid-State” Memory
•	ROM
–	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
Breaks
•	Option 1 (6:00-8:45)
–	10 minute break after the first hour
–	5 minute break after the second hour

•	Option 2 (6:00-9:00)
–	15 minute break after the first hour
–	15 minute break after the second hour

•	No food or drink in the teaching theater
Introductions
•	Over break:
–	Pair up with one person you don’t yet know
–	Introduce yourselves to each other

•	After break:
–	Introduce your partner to us
–	Name, background, goals, one interesting thing
System Architecture
“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, …
How Disks Work
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
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
Team Exercise
•	Form into groups of 4
–	Be sure you have someone who has used Excel before in your group

•	Answer question 1(d) from the Fall 1996 final exam (available on the course Web site)
RAID
•	Disks can fail in two ways:
–	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”
How RAID Works
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
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?
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
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
Discussion Point: What’s a Virus?
•	Characteristics
–	Initiation
–	Behavior
–	Propagation

•	Spyware

•	Detection
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, …
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
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
Course Goals
•	Conceptual
–	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
Some Motivating Questions
•	What are the technical implications for:
–	Privacy? 
–	Copyright?
•	How will digital repositories develop?
–	How will they interact with distance education?
–	What are the implications for archives?
•	How might electronic dissemination impact:
–	Roles of authors, publishers, and readers?
–	Access by disenfranchised populations?
Some IT Courses at CLIS
•	708D	Digital Library Implementation
•	708V	Information Analysis on the Internet
•	733	Networks 
•	715	Knowledge Management
•	790	Building Systems (programming)
•	793	Database Design 
•	796	Information Retrieval Systems
Instructional Staff
•	Professor: Dr. Doug Oard
–	Offices: HBK 4121G/AVW 3145
–	Email: oard@umd.edu (finds me anywhere)

•	Teaching Assistant: GoUn Kim
–	Labs in HBK 2101, times TBA
–	Email: gounkim@umd.edu

•	Teaching Theater Technician
Approach
•	Readings
–	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
The Grand Plan
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
Getting From Here to There
Syllabus
•	Master the tools in the first 8 weeks
–	2 readings and one homework most weeks

•	Explore integrating issues the last 6 weeks
–	1 reading each week + the project
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
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
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
Course Materials
•	Textbook
•	Supplemental readings 
•	Daily access to a networked computer!
•	A few floppy disks or a USB memory stick
Computing at Maryland
•	Computer Labs (IBM, Mac, Unix)
–	HBK 2105 (IBM and MAC, CLIS students only)
–	PG2:  24 hr WAM lab
•	Need an OIT  “pay for print” account
•	Dial-in access (Unix only)
–	College Park (301)209-0700 (3hr)/864-2087(15min)
–	Baltimore      (410)962-8865(3hr)/962-8867(15min)
•	WAM userid and password required
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
Saving Your Notes
•	First, save the Word file on your M: drive
–	Connect over the Web to pick it up
•	http://ttclass.umd.edu

•	If you have a floppy or a USB memory stick
–	Save the Word file again there

Obtaining Recordings
•	All classes recorded
–	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
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?