comp-202 co course overview ntr - mcgill university

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COMP-202Course Overview

CONTENTS:Focus of the Course and PrerequisitesOutline and TextbookCourse Structure and Grading SchemeComputer Lab Info and Required SoftwareCourse Communication

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COMP-202Intro to Computing I

(Section 2)

WELCOME!

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My name is...

• Maja• Miss Frydrychowicz (fri-dri-ha-vitch)• Professor Frydrychowicz• Dr.Frydrychowicz• Miss/Ma'am/Sir/Professor

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4COMP-202 - Course Details

Focus of the Course

• Introduction to computer programming– Basics of problem solving

– Essentials of program design and implementation

• Coursework will be done in a programming language called Java– Concepts taught in the course apply to other programming languages

as well

• Aimed at students with little or no background in programming and/or knowledge of computer science

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Demo: A simple Java program...

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Do you know how to iterate over a 2D array? Can you write a

recursive program?• If you have no idea what the above questions are

about, GOOD, you're in the right course.

• If you suspect you might be overqualified for COMP-202, e-mail your section instructor (in this case, Maja).– We might invite you to write a test so that you can transfer

to a more advanced course.

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Prerequisites

• Prerequisite: A CEGEP-level math course or equivalent

• For those who graduated from high school outside Quebec and thus never attended CEGEP: any upper-level math course

• In any case, the ability to think logically and rigorously is more important than calculus, algebra or trigonometry

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Course Schedule

• Basics of programming– Variables, simple calculations, basic input and output

– Methods / functions / procedures

– Branching structures

– Loops

– Arrays, reference types

• Object-oriented programming– Using objects

– Defining your own classes of objects

– Exceptions, File I/O

– Recursion

– Maybe more...

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Course Communication

• Course home page:– http://www.cs.mcgill.ca/~cs202/2011-01/

• myCourses (WebCT Vista):– http://www.mcgill.ca/mycourses

http://www.mcgill.ca/mycourses

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Course Structure

• Lectures (3 hours/week, compulsory)– Highlight key concepts; opportunity to practice and ask questions,

receive and give feedback, MAKE MISTAKES.

– Students are expected to complete readings (posted on course website) before class and actively participate in exercises.

– All material taught in lectures is examinable unless otherwise stated

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You Maja

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You Maja

Assignments!

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You Maja

Quiz!

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You Maja

Midterm!

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You Maja

Final Exam!

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Super Fun Activity: Interviews

• Walk around the room, talk to people (including Maja) and write down the name of:1. A person who has NEVER programmed before.

2. A person who is born outside of North or South America.

3. A person who is a 3rd-year undergraduate at McGill

4. A person who grew up in Montreal.

5. A person who is fluent in at least 3 (human) languages..

6. A person who has NEVER eaten poutine.

If you collect six different names that are not your own, you'll get some candy.

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Resources Outside of Class

• Tutorials (optional, but very useful)– Several sessions of each, offered at different times; go at most

convenient time for you

– Tutorials start Thursday! details to be announced on myCourses

– Most tutorials will take place in January to help you get started

• Office hours (2 instructors, 12-15 teaching assistants)– Approximately 25 office hours per week

– TA office hours start next week; details to be announced

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What to expect from teaching assistants?

Teaching assistants will:

• Provide you with constructive feedback about your assignments to help you improve your programming skills.

• Be well-prepared to help you understand course material and assignments during their office hours and on the myCourses discussion board.

• Grade each assignment before the next assignment is due.

• Will deliver well-organized tutorials that include interactive problem solving.

• Will arrive at their office hours and tutorials on time, or use the Google calendar and the discussion board on myCourses to announce any last-minute changes.

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Tutorials

• Purpose:– To reinforce material taught in lectures through examples and hands-

on exercises

– To enable you to familiarize yourself with software needed to complete coursework

• Led by a teaching assistant

• Take place in a computer lab

• Smaller groups, therefore more individualized attention

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Tutorial Topics

• Tutorial T1:– School of Comp Sci accounts, login / logout

– GNU/Linux desktop environment

– myCourses

– RText

– Writing, compiling, running a small Java program

• Tutorial T2: Variables, types, methods

• Tutorial T3: Conditionals and iterations, more methods.

• We'll add a few more advanced tutorials in later months as needed.

• Tutorials M and F: Preparation for the midterm and final examination, respectively

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Grading Scheme (1)

• 6 assignments: 28%– Each assignment is worth more than the previous

• Assignment 0: 2% (Released tomorrow, Due Wed Jan 12th !!!)

• Assignment 1: 4%





– All assignments count toward your final grade

– Best way to learn the material

– Each student has two “late days” to use during the semester

– MUST be done INDIVIDUALLY

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Grading Scheme (2)

• 1 in-class quiz: 4% (sometime between Feb 7 and 11)

• 1 midterm examination: 18% (March 3, Evening)– To be held outside lecture hours; written

– E-mail us if you have a conflict with another evening midterm!

• 1 final examination: 50%– Held during final exam session; written

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Plagiarism :(

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Recommended Textbook (free; available on course website)

• “How to Think Like a Computer Scientist”– Our lectures will not follow this textbook exactly, but you should

still read it.

– We particularly recommend the chapters about “debugging” your code. Really useful for your assignments.

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SOCS Computer Labs

• If you are officially registered in the course, you can create an account to use the computers on the 3rd floor of Trottier building

• Computer availability:– Computers in open areas: physically accessible 24 hours a day, 7 days

a week

– Computers in side rooms: physically accessible on weekdays 10:00 - 20:00, weekends 12:00 - 20:00

• Consultant on duty: weekdays 10:00 - 20:00, weekends 12:00 - 20:00

• Computers run GNU/Linux (Unix-like OS), not MS Windows– Unix seminars are offered by SOCS Systems staff

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Required Software

• You are encouraged to use your personal computer or laptop to complete course work

• Software used in this course– Required: Java Development Kit (JDK)

– Optional: RText, Eclipse (later in the course)

• See course outline for details on how to obtain the above software packages

• All programs you submit for assignments must compile and run using JDK 6 or later– JDK is backward compatible; programs that compile and run under

previous versions also compile and run under JDK 6

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Useful Tips

• Read everything carefully: slides, notes, textbooks, instructions, assignment specifications, documentation, announcements on myCourses, ...

• Do not wait until the last minute to do your assignments or submit them

• Do not fall behind; each new concept builds on previous ones

• Contact instructors / TAs if you have difficulties

• Do not expect to be given every single detail; you will have to look things up in the provided material and deduce some things on your own

• Experiment!

• Practice makes perfect!

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Anonymous Survey

• Answers the following questions1) Why did you register for this course?

2) What are the qualities of a good teacher?

3) Maja's always looking for new music: what song/band/artist would you recommend?

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COMP-202 Introduction

CONTENTS:What Is Programming?How a Computer WorksProgramming Languages

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Part 1: What Is Programming?

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31COMP-202 - Introduction

Programming and Computers (1)

• In order to understand what programming is, we need to know what a computer is

• A computer is a machine that executes lists of instructions– We feed a list of instructions to the computer and the computer

executes them

– Takes “input”, produces “output”

• Programming a computer involves two things:– Designing lists of instructions that will make the computer solve

specific problems

– Having the computer execute the instructions

• The purpose is to have the computer solve the problem for you instead of you solving the problem by hand

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Cooking Scrambled Eggs (1)

• Input (things we need to follow the instructions):– Two eggs

– A tablespoon of oil

– A pan

– A stove

• Instructions:– Add oil to pan

– Heat pan on stove

– Crack eggs into pan

– Mix until light and flaky

• Output (things that result from following the instructions):– Scrambled eggs

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Counting Cards of a Given Suit (1)

• Input:– The deck

– The suit we are looking for

• Instructions:– Take a blank piece of paper

– As long as there are still cards in the deck that we have not looked at, do the following:

• If the current card is the card belongs to the suit, make a mark on the piece of paper

• Move on to the next card in the deck

– Number of cards that belong to the suit = number of marks on the piece of paper

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Counting Cards of a Given Suit (2)

• Output:– The number of cards in the deck that belong to the suit

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Ambiguous Instructions

• Suppose your cousin is not very creative and follows your instructions exactly– What happens if you forget to mention some details?

– What happens if you change the order of the instructions?

• For example, in the instructions for cooking scrambled eggs:– To what temperature should one "heat the pan on the stove"? Does it

matter? What will a person following the instructions do if it matters but it's not specified?

– What happens if one tries to "mix until light and flaky" before "cracking the eggs into the pan"?

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Exercise: parity of sheets in a stack of paper

• Your “computer” is a person who does not know how to multiply/divide/add/subtract and does not know what “odd” or “even” mean. The person is in an empty room and doesn't have access to any tools or devices.

• Individually, write down instructions for determining whether a stack of paper has an even or odd number of sheets.– What is the input and output?

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Instructions and Precision

• The instructions for finding a card in a deck or counting the number of cards of a given suit in a deck are very precise and unambiguous

• Your 6-year old cousin (or anyone else) will be able to follow them and arrive at the solution, even if– he / she has no creativity or imagination

– he / she has no ability to fill the gaps in your instructions (because you did not leave any gaps in your instructions)

– he / she does no understanding of the purpose of your instructions or what they are supposed to accomplish, and does not care

• Writing lists of instructions like these is the very essence of programming a computer

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Programs (1)

• Programs are essentially lists of instructions that tell a computer how to accomplish a task– Each instruction tells the computer to do something: an action, a

calculation, a comparison

• However, the computer does not understand the instructions or their purpose, it merely performs them without question

• Therefore, your instructions must be precise– The computer cannot fill the gaps if you forget to specify certain

things

– In those cases, it will either return the wrong result or choke

• Your instructions must also be ordered correctly– The computer will not be able to detect incorrectly ordered

instructions

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Programs (2)

– Again, in those cases, it will merely return the wrong result or choke

• Programs also have:– Input (things that they work on)

– Output (things that they produce)

• But programming a computer consists of more than just writing precise and unambiguous lists of instructions...

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Computer Languages

• The computer does not understand English or any other human language

• Therefore, not only must your lists of instructions be precise and unambiguous, they must be translated from human language to a language the computer understands

• Learning this language is similar to learning a foreign (human) language, but there are important differences

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Natural vs Formal Languages

• All languages that computers understand have a special structure which ensures that no valid statement expressible in these languages is ambiguous– Each statement has one possible meaning and only one possible

meaning

– Compare to the following English sentences:• "The lady hit the man with an umbrella"

• "Time flies like an arrow"

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Complex Tasks

• Sometimes, we want the computer to perform complex tasks

• Writing a detailed list of precise instructions for this complex task would be very difficult– There are just too many instructions for humans to manage

• Solution:– Break down the complex task into a series of simpler tasks; if the

simpler tasks are still too complex, break them down into even simpler tasks

– Write a list of instructions for each of the simpler tasks

– The list of instructions for each of the simpler tasks can be used as a single instruction in the list of instructions that performs the original task

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The Bank Machine

• A bank machine has a lot of functionality:– It checks whether you are who you say you are

– It gives you a choice of operations

– Each operation does something different

– It ensures that you satisfy the necessary conditions to perform the operation you have selected

• Let's try to break this complex task down

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The Bank Machine: Login

• Input– The customer's bank card

• Instructions:– Set the number of login attempts to 0

– As long as the number of login attempts is less than 3, do the following

• Read the PIN from the keyboard

• If the PIN matches the one associated with the bank card, then success, otherwise, add one to the number of login attempts

– Failure

• Output– Success if the login succeeds, failure otherwise

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The Bank Machine: Main Program

• Input:– The customer's bank card

• Instructions:– Perform Login subprogram

– If failure, keep the bank card and wait for next customer; otherwise• Ask user for operation

• As long as operation is not exit, perform subprogram associated with operation and ask user for another operation

• Return bank card and wait for next customer

• Output:– (Depends on the operations requested by user)

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Software

• Is a software package merely a program?

• Software typically consists of many subcomponents, modules, and subprograms

• Each subprogram solves a particular problem or performs a particular task

• Software also includes some information to be used and manipulated by the subprograms– For example, in a currency conversion program, it includes a table

with exchange rates

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Goals of This Course (1)

• To learn how to design and write precise, unambiguous, and detailed lists of instructions that can be used to solve a problem or perform a task– Requires imagination, rigor, and understanding of how we solve the

problem "by hand"

• To learn how to translate these instructions into a language the computer can understand– Requires remembering the "words" of this language, how they are

"spelled", what they mean, what the "grammar" and "punctuation" rules of this language are; similar to learning a foreign (human) language

• To learn how to deal with complex problems or tasks by:– Breaking them down into smaller subproblems or subtasks

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Goals of This Course (2)

– Writing subprograms which solve each subproblems or perform each subtask

– Connecting the subprograms that solve each subproblem or perform each subtask to form one program which solves the original complex problem or performs the original complex task

• In short, to learn how to develop software

• At the end of this course, you will be able to write a program that simulates a bank machine (and many other things)

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Part 2: How a Computer Works

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Hardware and Software (1)

• A computer system consists of both hardware components and software

• Hardware consists of the physical, tangible parts of a computer– Cases, monitors, keyboard, mouse, chips

– Rule of thumb: If you can take it in your hands and it is part of a computer system, then it is hardware

– It is the hardware which executes the instructions

• Software: Programs and data that they use

• A computer requires both hardware and software– Software cannot run without hardware; instructions are useless unless

they are performed by someone / something

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Hardware and Software (2)

– Hardware will not do anything without software telling it what to do

– Therefore, each is essentially useless without the other

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A Personal Computer

Monitor /screen(output)

Speakers(output)

Keyboard (input)Mouse(input)

Case;contains:•CPU•Memory•Disk drives•...

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taking notes; packing a box

remembering what Maja said 2 minutesago

remembering your name

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Central Processing Unit (CPU)• The "operation/action" part of the

computer's brain– Basically controls the information / data in a

computer

• Perform instructions– Arithmetic operations

– Logic operations

– Decisions

• The instructions it understands are much simpler and fine-grained than those we have seen in previous examples

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Memory

• Memory holds the data– Think of a filing cabinet

• Main memory: Most of it is called RAM, which stands for Random-Access Memory– Data has to be in main memory so that the CPU can access it

– Volatile: its contents are lost when the program terminates or when the computer shuts down

• Secondary storage: Hard drive / CD / DVD / Blu-Ray disc / USB memory stick– Persistent: its contents will not be lost when the computer shuts down

– This is where you keep the data for long-term storage

– Secondary storage has much slower access times than main memory

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taking notes; packing a box(CPU)

remembering what Maja said 2 minutesago (RAM)

remembering your name (secondarystorage)

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Summary

• Computers are machines that execute programs.

• A program is a precise list of instructions that may take input and make produce output.

• Dividing programs into subprograms is really useful for writing large, complicated software.

• The CPU is the part of the computer that executes instructions from a program.

• Program execution relies on a combination of working memory (RAM) and long-term memory (e.g. a hard drive).

comp-202 co course overview ntr - mcgill university

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