An “enjoyable” introduction to Programming

Dr. Jeyakesavan VeerasamySenior Lecturer

University of Texas at Dallasjeyv@utdallas.edu

Programmable device?

What is programming?

• Set up parameters such that same device can be made to do several different things.

Why learn programming?

• Automation continues…• Computer touches our lives more & more

every day…• More component based programming

always room for simple programs to do large tasks!

Learning to ride bicycle

• Difficulties for beginners:

• Difficulties for experienced folks:

Solution

• Training wheels• Helmet

• Makes learning enjoyable and safe!

Learning to program:Difficulties for beginners

1. Syntax errors • struggle for hours to fix syntax errors• Loose confidence • Frustrating experience• Run away & never come back if possible!

2. Logic errors Not a serious issue.

Difficulties for experienced programmers

Logic errorsContinuous learning

Solution

• Visual Programming Tools to teach programming concepts without encountering syntax errors

Introduction to Alice

• Developed at Carnegie Mellon University and available freely for every one!

• Website: www.alice.org• Alice 2.2 Software

Programming Concepts

A few examples

• Recipe to make your favorite food• Assembly instructions for a toy• Coming to college from homeWhat is common about these activities?

Programming concepts:Sequence structure

instruction 1;instruction 2;instruction 3;…

A few more examples

• Study at home or play cricket with friends?• Eat Parotta or Poori?• Go to Vijay’s movie or Karthik’s movie?• Go to job or go for higher studies?What is the common thing here?

Selection structure

IF condition is true THEN do this;ELSE do that;ENDIF

A few more examples

• Eat chips from a packet• Go on a shopping spree with lot of cash!• Take an exam that has several questionsWhat is the common thing here?

Repetition structure

WHILE (more items to process) process the next item;ENDWHILE

FOR month = 1 to 12 do monthly processingENDFOR

Object Oriented Programming (OOP)

• Models the real-world better

Purpose of Alice

• Enjoyable introduction to Programming• Natural introduction to OOP• Learning to program with training wheels• Stepping stone to learn more serious

languages (C/C++/Java)

Hands-on Introduction to Alice

It is a good idea to save each program separately so that you can

go back and review later.

Alice environment

• World• Gallery• Creating the initial scene– Adding objects– Working with objects

Program #1: Choose your favorite object from the gallery and make it an interesting setup.

10 minutes?

Our first program!

• Sequence structure• do a few interesting actions!

Program #2: Make your object do a few funny actions!

10 minutes?

Program #3

• Introduce multiple objects• do a few interesting actions!

Program #3: Make your objects do a few funny actions!

15 minutes?

Program #4

• Use DO TOGETHER structure• Add realism & sophistication!

Program #4: Use DO TOGETHER to do multiple things at same time!

20 minutes?

Program #4a

• Add Vehicles/Seaplane from local gallery.• Make it do loop the loop.• Use DO TOGETHER structure– seaplane move forward– seaplane turn backward– seaplane’s propeller roll right

• Use “style = abruptly” to make the motion smooth

Program #4a: Use DO TOGETHER to make the plane do loop the loop!

20 minutes?

Program #5

• Introduce repetition – counted loop• do a few interesting actions!

Program #5: Make your objects do a few funny actions multiple times!

10 minutes?

Program #6

• Use condition to stop the loop.• do a few interesting actions!

Program #6: Make your objects do a few funny actions multiple times, but stop when a

particular condition is met.

15 minutes?

Program #7

• How to do realistic walking?• Leg & body movements• Better to do with human objects• Create new methods

Program #7: Practice human walking/running animation

15 minutes?

Program #8

• Walking back and forth between 2 points?• Discuss the ideas before coding!• Use methods?

Program #8: Practice human walking/running back & forth.

15 minutes?

Program #9

• Alternate implementation of Program #8 using IF statement

• Variables• Decision statement

Program #9: Practice variables and decision structure

15 minutes?

Logical thinking

• You have been introduced to several building blocks – a few more on the way too.

• Now, it is all about putting/using them together in various combinations.

• I encourage you to think in high level, note down a few ideas (design), then proceed to implementation.

• Direct coding is NOT recommended.

Program #10: Lists/Arrays

Arrays cannot expand during run-time, but lists can. Alice supports more functionality with lists too. In simple words, lists are more powerful.

• Make a list of your favorite objects (multiple copies of an object is ok too!)

• Make them do something one at a time.• Make them do something in random order• Make them do something in sync.• You are not limited to these - use your imagination!

Program #10: Play with lists & practice each one.

15 minutes?

Event-driven programming

• Deletion of individual methods or objects possible - just drag it to Trashcan!

• We will cover event driven programming today.• Analogy: handling interruptions when you are

watching a movie or studying hard for an exam.• Related note: Time management is very crucial

in modern life.

Program #11: Events

• So far, we did all the work under “my first method”.

• But when it comes to games or complex apps, user may press various buttons/items & we need to respond to each event.

Program #11: We will start with a coach and a ball. Coach keeps doing some exercise. We will use key based events to move a ball to top of his head. Then, coach should stop exercising and do something funny.

15 minutes?

Program #12: Frog’s jumping game!

• Swimming pool – moving lilypads – make the frog to jump on lilypads carefully and reach other side to win!

• Make the lilypads to move independently back and forth first. Then, work on the game.

• If the frog jumps and touches the water, it will sink! I guess this frog does not know to swim

• Plan and write the pseudocode first, before coding!

Program #12: Frog jumping game. Discuss/share ideas with your neighbour and help each

other to progress …

Move frog 0.7 meters forward when up-arrow is pressed.For moving lilypads, use distance (pool width – cricle width) with bit random speed.Use vehicle property to stick to lilypad.

High level idea/pseudocode #1move the frog by 0.7 meters.IF index is beyond lilypads

declare win!ELSE

IF frog is close to circles[index]frog is safe set vehicle for frog to corresponding circleELSEfrog dies! – make frog disappeardisplay a messageENDIF

ENDIF increment index

High level idea/pseudocode #2move the frog by 0.7 meters.IF frog is close to “finish” object, declare win!ELSE

IF frog is close to any of the moving circlesfrog is safe set vehicle for frog to corresponding circleELSEfrog dies! – make frog disappeardisplay a messageENDIF

ENDIF

Transition to C/C++/Java

• Most of you have become “mature” Alice programmers – you can see the limitations of Alice now.

• Now that your fundamentals are bit strengthened, this is a great time to get started with C/C++/Java!

• Time management is crucial – I encourage you to spend a few hours to solve programming problems periodically to strengthen your skills.

Transition to C/C++/Java: Math Practice program

• You can program the following problem in Alice or C/C++/Java or both.

• Display 2 random numbers (limit the range for each number to 1-100) and ask the user to multiply manually & input the result. Verify whether the user input is correct. Repeat it for 10 times, keep track of the score and display it in the end like this:

Your score: 8 correct, 2 incorrect.

Transition to C/C++/Java: Guessing Game

• First, guess a number between 1 and 100. Then, your program should ask you a series of questions and determine your guess based on your answers.

Question format: How about NN (<,=,>)? • Develop the high level idea first.

Pseudocodeinitialize low = 1, high = 100WHILE low < high

mid = (low + high) / 2ask the user how about mid?IF user response is <high = mid-1ELSE IF user resposne is >low = mid+1ELSE IF user response is =print great!break;

IF low == great print “Your guess is” low

ENDIF

Sample run #1 (user input in RED)

Guess a number between 1 and 100 (both inclusive)and get ready to answer a few questions.How about 50 (<,=,>)? <How about 25 (<,=,>)? <How about 12 (<,=,>)? >How about 18 (<,=,>)? >How about 21 (<,=,>)? <How about 19 (<,=,>)? >Your guess is 20.

Sample run #2 (user input in RED)

Guess a number between 1 and 100 (both inclusive) and get ready to answer a few questions.How about 50 (<,=,>)? >How about 75 (<,=,>)? <How about 62 (<,=,>)? >How about 68 (<,=,>)? =Your guess is 68.

Reverse Guessing Game

• Play the reverse game. Computer should guess a number between 1 and 100. Now, you should ask questions & determine that number.

• C/C++: use srand() and rand() to generate random numbers

• Discuss the algorithm first before coding!

Pseudocodeguess = Generate a random number 1 … 100Ask for user inputWHILE user input != guess

IF guess < user input output “<“

ELSEoutput “>”

Ask for user inputOutput “You guessed it right. Good game!”

Sample run

I have guessed a number. You can ask questions now.50<25<12>

18>21<19>20=Good job!

References

• Alice website: www.alice.org• Textbook: Learning to Program with Alice by

Wanda Dann, Steve Cooper and Randy PauschISBN: 0-1318-7289-3

• Ebook: http://www.dickbaldwin.com/tocalice.htm