On Teaching Introductory Programming

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On Teaching Introductory Programming

• Abhiram Ranade

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Background

• I recently taught the IITB introductory
  programming course, CS 101.
• 700 students, varying preparation
• 60 Teaching Assistants
• Lack of a good textbook
• All usual teaching related issues content,
  delivery.
• Report of personal experience.
• Main focus content and delivery

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Outline

• The new student
• Basic Premises on learning motivation, fun.
• Course Themes
• Graphics
• Every lecture must solve a nice problem
• Depth helps learning
• Connect to other disciplines
• Cool Algorithms/Fun
• Concluding remarks

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The New Student

• Less reverent than 20 years ago
• More oppressed in school years, expects more
  freedom in college.
• Wants to know why he/she should learn what is
  being taught
• Is swayed by immediate gratification.
• Has many distractions

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Basic Premises on learning

• Motivation must be very clear
• The student must develop ownership of the
  questions being answered in the course
• Topics must be fun!
• Beauty vs. Utility? Beauty and utility.

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Fun

• Eating ice cream
• Climbing a mountain
• Swimming or playing a sport
• Seeing a movie, natural panorama
• Seeing a magic show
• Learning should have all kinds of fun!

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Fun and programming

• Sense of accomplishment students should be able
  to do something significant of interest to
  themselves.
• Should relate CS to other sciences, even life!
• Should be surprised by cool algorithms. Must be
  occasions of Wow!.

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Theme 1 Graphics Turtle Geometry

• Available to students, from lecture 1. Used to
  teach many concepts
• Notion of program as sequence of instructions.
• Iteration repeated patterns
• Recursion recursive patterns
• Procedures draw_house()
• Graphical debugging
• Visualization Trees, Newtons method for finding
  roots.

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Turtle Geometry Graphics (contd)

• Class heirarchy

Shape
Polygon
Circle
Line
Turtle
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Introductory Lecture

• Traditional Printing Hello world
• Lots of syntax with little excitement.
• Instead use graphics package to draw nice
  pictures. Non trivial picture drawing exercises
  from day 1.
• Lecture 1 sets the tone of the course.

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Theme 2 Begin with a problem

• Every lecture begins with a probleme g. we want
  to plot movement of gas particles on the screen.
• Can we do this using the language we know so far?
  No.
• Here is a new statement/concept which will help.
• Not Today we will learn about arrays..

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Theme 3 Depth helps learning

• For every concept have
• good motivating examples
• discuss implementation, e.g. recursion, pointers
• interesting programming exercises.
• Generalization helps learning
• pointers lists are good, but trees really force
  you to learn!
• Mix ideas Use graphics to draw out trees
  recursively...

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Connect to Other Disciplines

• Newtons method
• Simulate movement of charged particles
• Hemachandra (Fibonacci) numbers as they arise in
  counting the number of different possible poetic
  meters of n beats.

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Cool Algorithms

• Newtons algorithm
• Searching trees visualize with turtle moving on
  the screen.
• Shortest paths good combination of
• matrix multiplication over , min
• C supports representation of infinity
  HUGE_VAL gt very elegant, short code for
  computing shortest paths
• Students feel they are improving their math!

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Fun!

• Graphics package includes X windows event loop
  wait for event to happen and based on event do
  whatever.
• Used by many students to develop video games in
  final project
• Did not talk about event driven programming,
  listeners etc. because too much syntax.

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General Remarks

• Carefully designed lab exercises. TAs graded
  them. Final weightage of labs was less because
  of fear of copying.
• Students liked assignments and said they helped
  learn.
• Switched to writing on board (tablet) because of
  student demand. Students said lecture developed
  better than slides.
• Some students found the course too mathematical.

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What I would have liked to do but didnt

• String class examples
• Assertions, reasoning about programs..
• STL and algorithms class use.
• Programming style
• Debuggers/IDEs.
• Would have been possible with 3 lectures/week.