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CPSC 111Introduction to Computation

May 4, 2009


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Who I Am

Your instructor is

Kurt [email protected]

ICICS 233

office hours soon to be determined

(but come on in anytime the

door is open)


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What This Course Is About

Calendar description: Basic programming constructs,

data types, classes, interfaces, protocols and the design

of programs as interacting software components.

Prerequisites: Mathematics 12.

Ignore the buzzwords for now. Youre going to learn

about computers and how to put together

sequences of instructions to make them do useful stuff.


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Who this course is for...

Although it is expected that you will have used a computer

prior to taking the course and that you are familiar with

basic keyboard and mouse operations, no prior

programming experience is assumed. This course willteach you basic programming constructs that will allow

you to unleash your creativity and develop your own

applications software.

In other words, you can succeed here even if you havenever ever written a computer program.


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...but note this

If you have already received credit for CPSC124 and

CPSC126 or for CPSC122 and CPSC128 then you

cannot receive credit for CPSC111. If you have taken

CPSC124 but not CPSC126 then you must takeCPSC111 in order to advance through the computer

science program. If you have taken CPSC122 but not

CPSC128, please consult with a department advisor.

This probably isn't relevant to any of you. The importantthing to know is that you must have taken Mathematics 12

before now, or you'll most likely be dropped from the

course.


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Administrative Stuff

Your textbook is Big Java by Cay Horstmann

(Wiley and Sons). The third edition is in the

bookstore, plus some copies of the second edition.


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Your textbook is Big Java by Cay Horstmann

(Wiley and Sons). The third edition is in the

bookstore, plus some copies of the second edition.

You should get a copy of either one. Seriously.

Read chapter 1 and chapter 2 before Wednesday.


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Tentative schedule

First midterm exam: Friday, May 15 (in class)

Second midterm exam: Friday, May 29 (in class)

Final exam: Friday, June 12 (in class)

Tentative grade calculation (subject to change)

Quizzes 5%

10(?) labs 10%

5(?) assignments 10%

First midterm 10%Second midterm 20%

Final exam 45%


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I post all my PowerPoint slides on our WebCT page.

We're using the new WebCT Vista (www.vista.ubc.ca).

I post the slides sometime (not instantly) after class, not

before. Our WebCT pages should be available today.

Until you get up to speed with WebCT (in lab) you can

find out more about CPSC 111 at

http://www.ugrad.cs.ubc.ca/~cs111/. Note that the

"outline" and "schedule" sections are not up to date yet --

they describe the section that ended Friday. We'll tryupdate those pages within the next 48 hours. But please

read the "policies" section.


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No labs or tutorials today.

Labs and tutorials begin on Wednesday of this

week, then on Friday, then every Wednesday andFriday thereafter.* You should do Lab 0 (a take

home lab) as soon as WebCT for 111 is ready.

Typically well use the entire 2.5 hours every

Monday, Wednesday, and Friday, with a ten

minute break somewhere in the middle. That

break is for me as well as you.

* Except possibly on exam days.


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Lab work is marked by your TAs at the lab.

Those marks impact your final grade.

Tutorial work is not marked, but skipping tutorialsis not a good idea.


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How intense is the summer version?

3 lectures per week x 6 weeks = 18 lectures

3 exams: subtract 3 lectures = 15 lectures

1 holiday: subtract 1 lecture = 14 lectures

In the winter, this class runs 13 weeks. So in the summer,

we have 14 lectures to cover 13 weeks of material. One

lecture in the summer is almost a week's worth of material

from the winter session. Do not fall behind.

Oh, did I mention that your first midterm exam is next week?


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More Administrative Stuff

Please note that in order to pass the course you must:

obtain an overall grade of at least 50%

obtain a grade of at least 50% on the final exam

obtain an overall grade of at least 50% on the combined lab and

assignment grades

If you fail to satisfy any of the above criteria, a grade no greater than

45% will be assigned in the course. The instructor reserves the right

to modify this grading scheme as necessary throughout the term.

Note that you will not pass the course if you are not enrolled in a labsection. More lab seats will be added very very soon.

Thats enough administrative details for now. There will be more

details to wrestle with in the days to come.


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This is a first course in computer science...

...but what is computer science?

"Computer science is as much about computers as

astronomy is about telescopes."

Edsger Dijkstra


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Computer science revolves around computational

processes.... A process is a dynamic succession of

events.... When your computer is busy doing something,a process is going on inside it.

Oliver Grillmeyer


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Computer science is the study of what computers do, not

of what they are.

me


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Processes, procedures, and programs

A process is what happens when a computer

follows a procedure - its a procedure in execution.

A procedure is a collection of instructions in somemeaningful order that results in useful behaviour

on behalf of the device that executes the

instructions.

When the instructions are written in a symbolic

language that can be executed by a computer, the

procedure is called a computerprogram.


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Processes, procedures, and programs

What we do in CPSC 111 is

think in terms of procedures

use a programming language called Java

to write the procedures as computer

programs

and execute the programs on a computer

to generate useful processes


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Procedures and algorithms

Computer people often use the words procedure

and algorithm interchangeably...we will too.

An algorithm is

a finite procedure

written in a fixed symbolic vocabulary

governed by precise instructions

moving in discrete steps, 1, 2, 3, ...

whose execution requires no insight, cleverness,

intuition, intelligence, or perspicuity

and that sooner or later comes to an end

David Berlinski in The Advent of the Algorithm


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Lets dive right in and write a procedure or

algorithm, just for fun.

Well make a peanut butter and jelly sandwich.

(Is anyone here allergic to peanuts? You should go

way to the back of the room.)

Form a small group with your neighbours. Grab

some paper and a pen, and write down how to

make a peanut butter and jelly sandwich as a

sequence of steps. Number each step. Bring me

your procedure when youre finished.


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Was my interpretation of your instructions a little bit

frustrating?

If telling me how to make that sandwich had been

really important to you, you might be quite upset

right now.

Getting other people to do what you want them to

do isnt easy. Getting computers to do what you

want them to do is less easy -- a lot less.


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Heres why we get frustrated when we start to learn

to write programs to make computers do stuff:

An algorithm is

a finite procedure







We dont have a lot of practice at being precise!


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Heres why we get frustrated when we start to learn

to write programs to make computers do stuff:

An algorithm is

a finite procedure







We dont have a lot of practice at working with stupid!


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Why working with stupid isnt easy

The languages that computers understand are very different

from the languages that humans understand, and for good

reason.

Unlike computers, humans bring enormous amounts ofknowledge to bear on the simple problem of figuring out

what just a single sentence means.

You may not be able to articulate the knowledge that youre

using, but you do have it, and you can apply it in real time,as you read or listen, even if the sentence is one you've

never encountered before. (Like the one you've just read.)


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So why is that important to you, the budding young computer

programmer?

Because the natural language you use, whether English,

Chinese, French, Klingon, or whatever, is highly ambiguousand you deal with it automatically and unconsciously. Every

sentence you write, every utterance you speak, lacks

precision (to say the very least) and you count on the

understander on the receiving end to disambiguate it without

even a glimpse of recognition that the disambiguation ishappening. Its an inherent trait of natural language and the

humans who understand natural language.

Its what we do. It sets us apart from everything else.


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But imagine that youve been transported to a world where

the other inhabitants cope with ambiguity even less well than

I did when I tried to follow your instructions for making a

sandwich. A world, in fact, where they dont cope with

ambiguity at all, a world where they bring almost noknowledge whatsoever to bear on the problem of

understanding what youre saying. How painfully tedious

would that be?

You dont have to imagine it -- youre going to be living in itfor the next six weeks. Its the world of computer

programming. Welcome to our world.


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How to avoid frustration

Practice, practice, practice.

This material isn't conceptually incomprehensible, but...

It takes a lot of practice to learn to be precise enough tomake a computer do what you want

It takes a lot of practice to keep from assuming that the

computer is smarter than it really is

It takes a lot of practice to get good at this stuff


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Dont try to game the system. It wont work for most of you.

Your presence at the big university means youve mastered

the art of cramming for exams, writing term papers the night

before theyre due, and so on. It works with subjects whereyou have years of experience, but it doesnt work so well

where you have no previous experiencelike in this course.


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Learning to write computer programs is similar to learning to

play a musical instrument or write stories. Its a skill. Skill

requires practice.

You wouldnt put off all your piano practice until the nightbefore your recital.

You dont want to put off all your programming practice until

the night before a programming assignment is due or (worse

yet) until the night before your exam.

Practice, practice, practice.


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Study your book frequently, dont just read it. (Recent

studies suggest you should read, then close the book and try

to write a summary of what you've been reading.)

Play with the programs from your book and from class.Type them in, run them, change them, run them, repeat.

Go to the labs.

Go to the tutorials.

Ask questions.

Do more than we require. Practice, practice, practice.


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Dont wait until the last minute to get help


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Bad things happen while learning a new skill. Start

homework early; give yourself time for mistakes.

Hey, can I still passif I can get enough

partial credit?


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Dont be too ambitious with your course load. You cant

slack off in this class, even for a few days.


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So what will you learn here?

How to get a computer to do your bidding:

How to represent solutions to problems as

procedures or algorithms

How to represent those procedures as

programs written in a programming language

How to get the computer to turn your programs

into processes that do useful stuff


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Why should you learn it?

If youre one of the few computer science majors

enrolled in this class right now, the answer should

be obvious.

But what if youre not a computer science major?

As an informed citizen, the more you know about

how these machines work, the better youll be

able to weigh in on decisions that affect your life

in a very technology-dependent future.

Also, no matter what your chosen field of study


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Thinking in terms of process is crucial

formulas are no longer sufficient for describing

how our world works. For example,

Economic systems are processes

Political systems are processes

How HIV invades cells is a process

How pharmaceuticals interfere with HIV is also a

process, and so on

Being able to think about complex systems in terms

of procedures and processes will be of value to you

even if you never write another program after 111.


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But wait, there's more*...

It's not obvious to you, but you're in the middle of a

revolution. Think about the changes that have

happened already...

This computer from the 1950s had roughly the

computing power of today's musical greeting cards.* most of the following examples have been stolen from Ed Lazowska's very inspiring

2008 SIGCSE keynote address. Thanks Ed.


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But wait, there's more...



happened already...

The computing power that was aboard Apollo 11 on

its flight to the moon in 1969 can be found in a

Furby.


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happened already...

The power of my first computer in 1972 that served

a university and its surrounding business

community...


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happened already...

The power of my first computer in 1972 that served

a university and its surrounding business

community is exceeded by my iPhone.


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There are now roughly 1,000,000,000 PCs in the world (or 1

for every 6 people on the planet), yet that number represents

less than 2% of all the processors in the world. Where are

the others? Everywhere around you:

GPS systems

cell phones

DVD players

compact disc players All 50,000,000,000

iPods of these processors

calculators execute programsdigital cameras

automobiles

household appliances

children's toys

and so on...


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In 1995, a group of computer science experts tried to

anticipate where computer science research was going.

Here are some of the things they missed:

entertainment technologydata mining

portable communications

the World Wide Web

speech recognition

The ways in which people put computing technology to use

continue to astound the experts.


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Advances in computing have already changed the way we

live, work, learn, and communicate in ways most people

couldn't have imagined.

Advances in computing drive advances in nearly all otherfields (see biology, for example).

Advances in computing drive our economy (especially

through the uptake of computing by traditional industries

making them more efficient).


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What's coming? Just imagine...

much greater understanding of our environment (e.g.,

wide-spread remote sensor oceanography)

comprehensive energy management solutions

automobiles that don't/can't crashindividualized education

neurobotics

nanomachines in medicine

robotic care-givers

personalized pharmaceuticals based on individual genome

mapping


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It all starts here

While we love our computer engineering sisters and

brothers for continuing to make computers smaller and

more powerful at the same time, all the advances we just

talked about depend on software: the computer programs

that make the machines do something useful.

And for almost everyone everywhere, the path to creating

that software starts in introductory computer science

classes in schools all over the world. You have to learn

some of the boring stuff before you can start building thecool stuff.

If you want to play an active role in the ongoing revolution,

this is where you begin.


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Data collection

In addition to turning you into incredibly powerful

computer programmers, we'll also be using you as

lab rats. We'll of course be using information from

your quizzes, homework, and exams to inform us

as to how to facilitate your understanding.

But we'll also be asking you to participate in other

data gathering efforts as well. We'll ask you to

answer questions on various surveys, including theone we'll hand out now. This particular survey will

help us determine how much programming

experience you already have.