Back to Basics in CS1 and CS2

1
Back to Basicsin CS1 and CS2

• Stuart Reges
• University of Washington

2
In a Nutshell

• Major redesign of the CS1/CS2 courses at the
  University of Washington
• New CS1 emphasizes procedural programming,
  objects later
• New CS2 includes OOP concepts and traditional
  concepts (recursion, linked lists, binary trees)
  with a collections theme
• Student satisfaction up enrollment up female
  admissions up

3

• I used to believe
• Programs with sophisticated graphics and GUIs
  would be more fun for CS1 students than console
  and file based programs
• I found
• They were often less fun
• I now believe
• Students enjoy writing complete programs
• Students prefer standard Java
• Graphics gets old fast
• Our sophisticated programs are fairly crude
• The problem solving challenge is more important
  than surface appearance

4

• Confession I have them write a program that
  produces this (console output, ascii art)
• /\
• //\\
• ///\\\
• ////\\\\
• /////\\\\\
• ../\..../\..
• ./\/\../\/\.
• /\/\/\/\/\/\
• \/\/\/\/\/\/
• .\/\/..\/\/.
• ..\/....\/..
• \/\/\/\/\/\/
• .\/\/..\/\/.
• ..\/....\/..
• ../\..../\..

5

• I used to believe
• I could teach object oriented design in CS1
  instead of procedural design
• I found
• Java objects involve a lot of syntactic detail
• There are no 50-100 line programs where OOD helps
• Many object based assignments end up being paint
  by numbers rather than problem solving
• Many students dont get the object concept
• I now believe
• A large number of mid-level students who can
  master procedural concepts (loops, conditionals,
  methods, parameters, arrays) struggle with the
  object concept
• Therefore, it is better to start with procedural
  programming if you have a broad audience

6
Confession I have my students write code like
this (with static methods) public class
DrawFigure public static final int
SUB_HEIGHT 3 public static void
main(String args) drawLine()
drawTop() drawBottom()
drawLine() // Produces a solid line
public static void drawLine()
System.out.print("") for (int column
1 column lt (2 SUB_HEIGHT) column)
System.out.print("-")
System.out.println("") ...
7
A few more CS1 details

• Students use objects early, define them later
• We use a custom DrawingPanel to explore objects
  (Graphics, Color, )
• Scanner is helpful for console and file input
• while (input.hasNextLine())
• String text input.nextLine()
• Scanner data new Scanner(text)
• ltprocess datagt
• Input files make programs interesting

8
Some objections

• Stuart is guilty of crimes against Java
• Ive been in trouble before
• Why not a procedural language like Python for
  CS1?
• Were using Java in CS2 and switching languages
  is tough for mid-level students
• Why do you have to use the s-word so much?
• Procedural Object Oriented Programming is a
  slippery slope (look what it spells)

9
A few words about CS2

• Eliminated some useful but less fundamental
  topics (GUIs, junit testing, javadoc, streams)
• Brought back emphasis on fundamentals (recursion,
  linked lists, binary trees) including recursive
  backtracking
• Less emphasis on OO design, but basic OO concepts
  included (encapsulation, inheritance, interfaces)
  including a client view of data structures
• Collections framework as a case study

10
Results student satisfaction
11
Results CS1 enrollment
12
Results female admission
13
Conclusions

• New courses are working for us
• Impossible to tell which changes have helped the
  most
• Too early to infer long-term trend (particularly
  with female admission)
• We serve as an existence proof that back to
  basics can work

14
For more information

• http//www.cs.washington.edu/homes/reges
• Building Java Programs by Stuart Reges and Marty
  Stepp, Addison Wesley, expected early 2007