CS221N, Data Structures

1
Introduction

• CS221N, Data Structures

2
Welcome to Survey!

• Introductions and Contact Info
• Syllabus
• Goals of the course
• Outline
• Contingency plans
• Chapter 1

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My Information

• Dr. Trevor M. Cickovski (Dr. C)
• Office Hours
• T 9-3
• H 9-1
• Office 115C Sheen
• Phone [phone]
• E-mail cickovtm_at_eckerd.edu

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Objectives

• This course is designed to give you a basic
  understanding of
• How a computer works
• What a computer can do

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Prerequesite

• None
• Assume no background in computers

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Textbook

• Nell Dale and John Lewis. Computer Science
  Illuminated Third Edition. Jones and Bartlett
  Publishers, 2007.
• We will cover (roughly) one chapter per week
• I encourage you to bring this to class
• Lectures will follow very closely
• We will often view examples from this text
• Recommend but do not enforce reading

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Labs and the Lab Manual

• R. Mark Meyer. Explorations in Computer Science
  Second Edition. Jones and Bartlett Publishers,
  2006.
• Friday will be the lab day
• Labs together will account for 50 of your
  grade!!
• Note You must show up
• The lab must be completed in the allotted 50
  minutes
• Ill be present to help

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Lecture

• Time MWF 1145-1235
• Room SE 102
• Slides
• Prefer interactivity in the lecture
• Highly recommend but do not enforce attendance
• Some slides will be purposely incomplete, which
  Ill fill in lecture either on tablets or the
  blackboard if they are not available.

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Exams

• Two Third-Term Exams (each 15)
• Friday 10/2, in class (week 5)
• Friday 10/30, in class (week 9)
• Final Exam (20)
• 1130 AM 230 PM on Wednesday 12/9
• SE102 unless you hear otherwise

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Topics

• Lets go through them together.

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Each Data Structure

• Note that there are a total of nine data
  structures well cover
• Arrays, stacks, queues, linked lists, binary
  trees, red-black trees, hash tables, heaps, and
  graphs
• Each of these represents a way of storing a
  collection of data
• For each of them
• Motivation
• Operations
• Efficiency
• Java Implementation

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Grade Breakdown

• A 92-100
• A- 90-91
• B 88-89
• B 82-88
• B- 80-81
• C 78-79
• C 72-78
• C- 70-71
• D 60-69
• F 0-59

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Hurricane Preparation

• The plan for this course is to continue
  operations best we can
• I will continue to post slides online
• We will continue to follow the syllabus (so bring
  it!)
• I will continue to follow the textbook (so bring
  it!)
• Homeworks will continue to be assigned and
  submissible over e-mail.
• Contact will be made as necessary

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Disability Accomodations

• Contact disability support services if necessary
• dss_at_eckerd.edu
• 8248 Edmunson Hall
• This applies to all kinds of disabilities
• Physical
• Cognitive
• Psychological
• Confidentiality enforced

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Missing labs and exams

• Eckerd has changed its policy regarding missing
  labs and exams
• Lets go through it together
• Much more trust on your shoulders
• Remember.
• Eckerd is small. There are RAs, other
  professors, coaches, people in your dorm, etc.
• If youre caught faking illness, you fail the
  entire course
• Your risk if you choose to do so

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The Honor Code

• Which youve seen before
• On my honor, as an Eckerd College student, I
  pledge not to lie, cheat, or steal, nor to
  tolerate these behaviors in others.
• Academic dishonesty can count as
  cheating/plagiarism
• Report will be submitted to registrar
• First offense Could fail the course
• Second offense Could be dismissed from the
  college

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The Honor Code

• When it comes to sharing solutions
• It is illegal to give
• It is illegal to receive and use
• Safest thing is to not give your solution to
  anybody
• You can trade ideas, but not answers
• Legal
• Heres an idea try this.
• Illegal
• Heres my writeup. Get ideas from it.

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The Computer

• We all use them!
• Most of us, probably daily
• Composed of three portions
• 1. Software, which runs on
• 2. Hardware, which manipulates and stores
• 3. Data

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Data

• All data stored in a computer can be broken down
  to 0 and 1
• Called binary format
• Which actually correspond to ON and OFF.
• If current is passing through a wire it is ON.

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Data

• We will see in this course, we can store ANY type
  of information in binary
• Numbers
• Characters (A-Z, a-z, etc.)
• Images
• Video
• Audio

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Hardware

• Controls the flow of electricity through circuits
• In a nutshell, control which wires are on and
  which are off.
• Hardware can only recognize information in binary
  (on/off).

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Software

• Consists of the set of programs which can
• Perform computations
• Manage data
• Programs that the user
• can run are often called
• applications.

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Hardware vs. Software

• Which do think are which?
• Processor
• Memory
• Microsoft Word
• Keyboard
• Minesweeper
• PowerPoint
• Mouse

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Writing Software

• Software must be programmed somehow.
• We know hardware can only recognize binary
  information
• But nobody writes programs in binary!
• Itd take forever and a day.

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Writing Software

• Software is written in a programming language.
• There are many C, Java, C, Python, Perl
• A software developer uses a programming language
• More understandable than binary
• Any theories why there are so many languages?

REM GET TWO NUMBERS REM FROM THE USER,
AND REM PRINT THE MAX INPUT X INPUT Y IF X
gt Y PRINT X ELSE PRINT Y
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Translating Software To Binary

• This is the job of a compiler.
• Sometimes this translation is done everytime you
  run a program, sometimes its only done once

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Translating Software To Binary

• Note Every programming language needs a compiler
  of some form
• Hardware cannot run programming languages, just
  binary

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Operating System

• The operating system is the one program which
  always runs when the computer is on
• Examples
• Windows XP
• Mac OS X
• Linux
• UNIX
• BSD

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Operating System

• The job of the operating system is to manage
  the other programs that are running
• Schedule the programs
• Multitasking
• Synchronize data access
• Manage memory
• Manage files
• Protection and security
• Networking

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To give you a little taste

• What goes on in software between when an M is
  pressed and when the character is displayed in
  Microsoft Word
• The key press interrupts the operating system
• Operating system transfers control to the active
  program, in this case Microsoft Word
• Microsoft Word receives M as input, and adds
  this character to the file that is open
• Microsoft Word transfers control back to the
  operating system
• When you throw hardware in, its even more

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Going back to hardware

• Lets take a deeper look at some of the hardware
  components and their functions
• Processor Executes instructions
• Memory Stores data
• There are many types of memory! Can we name
  some?
• Keyboard Take input from the user
• Mouse Take input from the user
• Printer Take output from a program, and print it
  on paper
• Deadhorse beat Hardware only understands binary!

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The Processor

• The job of a processor is the following
• Accept an instruction in binary
• Decode it
• Execute it
• Perform arithmetic, access memory, etc.
• Each instruction takes a certain number of cycles
  to execute
• Modern processors, avg is roughly 1 cycle per
  instruction

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The Processor

• When we say a computer has a 2.3 GHz processor,
  what does this mean?
• Hz cycles/second
• Giga 109
• So this processor executes 2.3109 cycles/s.
• Which if each instruction takes a cycle, 2.3109
  inst/s.
• Or 2 billion, 300 million.

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Memory

• Have we come up with some different types?
• There are actually five
• 1. Registers
• 2. Cache
• 3. RAM
• 4. Hard Drive
• 5. External Storage
• CD or DVD-ROM
• Flash Drive
• Floppy Disk

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Memory Volatile vs. Non-volatile

• Volatile memory loses its contents when the
  computer is turned off
• Non-volatile is preserved
• Registers, cache, and RAM are volatile
• They are used for temporary storage as programs
  execute
• Actually involve electrical current (remember
  ON/OFF?)
• Hard disk and external storage is non-volatile
• They are used for permanent storage
• Involve data being encoded into magnetic platters

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Memory Speed

• In order of speed
• 1. Registers
• 2. Cache
• 3. RAM
• 4. Hard Disk
• 5. External Storage
• However, each is successively larger.
• For example, you never hear of a computer having
  more hard disk space than RAM. But RAM is
  faster! Wouldnt we want more of it? Why not
  all registers??
• Theories?

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Memory Size

• What do we mean when we say a computer has a 200
  GB hard drive?
• 1 bit a zero or one
• 1 B 8 bits
• Giga 109
• So that means that our hard drive can hold
  200109 B, which is 8200109 bits.
• This is 1.6 trillion bits.

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Memory Size

• Question to ponder.
• Given what we know about RAM
• It is used temporarily as programs execute
• It is faster than hard disk
• It is also more expensive
• The size of a hard disk does not typically affect
  the speed of a computer. But the size of RAM
  does.
• Lets take a few minutes and think this through.
  Why might this be the case?

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In Summary

• Heres what happens when a program runs on a
  computer

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Abstraction

• Abstraction is a way of thinking about something
  which hides complexities.
• Essence of computing
• To drive a car, we need only know a few things
• Gas petal, brake petal, gear shift, mirrors
• But a lot actually happens under the hood
• We dont need to know that to drive a car
• By now, you should be realizing the same is true
  with a computer!
• Examples of abstraction? Weve been through
  some.