learning difficulties in computer programming by dr sc li

Learning Difficulties in Learning Difficulties in Computer ProgrammingComputer Programming

By Dr SC LiBy Dr SC Li

CS CurriculumCS Curriculum

ProgrammingProgrammingInformation Information ProcessingProcessing

Computer Computer SystemsSystems

Teaching SyllabusTeaching Syllabus

199920% 20% 60%

50% 20% 30%

Is Programming Is Programming becoming obsolete in becoming obsolete in school curriculum?school curriculum?

Pros & ConsPros & Cons

(+) Programming is a job skill, and that programming instruction should not be included in a general school curriculum

(-) Programming is a subject where one can learn effective problem solving skills

Pros & ConsPros & Cons

(+) Programming is a job skill, and that programming instruction should not be included in a general school curriculum

(-) Programming is a subject where one can learn effective problem solving skillsRelatively little empirical support

Relatively little empirical support

Case Study

What is(are) the root(s) of the What is(are) the root(s) of the problems envisaged by the problems envisaged by the student?student?

http://ited.hkbu.edu.gk/cs/session2/case.html

Problem with teaching and Problem with teaching and learning programminglearning programming

What are the problems of What are the problems of teaching and learning of teaching and learning of programming in local programming in local context?context?


The root of this problem lies in the beliefs that:

syntax is is the most important thing to learn in a programming course

student has had to waste the majority of his/her patience, concentration, and effort on keeping the syntax of my programs straight, leaving barely enough of these qualities to devote to solving the problem


It is hard for students to make any meaning out of the programming skills they have learned.

Inert KnowledgeInert Knowledge Example:

Geometry students typically understand each step in a proof, as the teacher puts it on the board, line by line.

They see their teacher develop a proof line by line, and not surprisingly, they think they should be able to do the same.

However, when attempting to do a proof for homework, students often have no idea where begin.

Inert KnowledgeInert Knowledge

Why? Do mathematicians develop proofs in

such an orderly, linear fashion?

Inert KnowledgeInert Knowledge

Mathematicians develop proofs in a nonlinear, search process.

Teaching ProgrammingTeaching Programming

Textbooks Textbooks

syntax and semantics of constructs in a language

focusfocus


Why should learning where to Why should learning where to put a semicolon in Pascal lead to put a semicolon in Pascal lead to enhanced problem-solving enhanced problem-solving ability?ability?

the lack of impact of programming on problem-solving

Focus on instruction of the syntax and semantics

Teaching ProgrammingTeaching ProgrammingProblem Solving

theories, rules,

operators, heuristics

initial state:

a set of symbolsgoal state

Problem ProductProcess vs.vs.


Research StudiesResearch Studies

A lack of heuristic in composing and coordinating components of a program

Learning difficultiesLearning difficulties

Problem-solving with ProgrammingProblem-solving with Programming

problem-solving skillsproblem-solving skills

ability to explore alternative ways (variability) of solving the same problem

-- Soloway (1988)

How variability is currently taughtHow variability is currently taught

Nice, clean, straightforward “step-wise” refinements of problem

students nod their heads at every step in the transformation but don’t see - because they are not shown - the myriad of design decisions that have been left out.

Textbook shows that only one decomposition is needed to derive a program, students believe that they too should only do one decomposition.

Structured programmingStructured programming


VariabilityVariability

FORFOR Loop Construct vs. Loop Construct vs. WHILEWHILE Loop Construct Loop Construct

TTEEXXTTBBOOOOKKSS

What is the student supposed to learn from this variability? When is one more appropriate than the other?

Students: Why then textbooks show both? Why

should I learn both structures when one is equivalent to the other?


In sum, the little variability that is explicitly shown in the majority of textbooks actually gives students the wrong idea of why variability is important: textbooks focus on the twiddles at the construct level.

It does not require the students to think about the problem in “radicallyradically” different ways.


Variability in Novice Programmer Variability in Novice Programmer Problem-solvingProblem-solving

poor solution

better solution

perturbation

(local)

(global)

To help novices break out of the local search (variation) to a global search of solutions:

Variability in Novice Variability in Novice Programmer Problem-solvingProgrammer Problem-solving

Solution Evaluation SkillsSolution Evaluation Skills Variability Exploration SkillsVariability Exploration Skills

Solution Evaluation Skills Novices need better evaluation skills so that

they can better characterize and differentiate “poor” solutions from “better” solutions.

Variability Exploration Skills Novices need to understand the sources of

variability that precede simple twiddling with language constructs, for the ability to generate “radically” different solutions resides lies in the skill of exploring alternatives in those earlier problem-solving phases


Phases in the Novice Program Generation Process

Understand problem specification Decompose problem into programmable

goals and objects Select and compose plans to solve problem Implement plans in language constructs Reflect - Evaluate final artifact and overall

design process


Rock-paper-Scissors Problem: Rock-paper-Scissors is a two player game.

Each player simultaneously makes one of three possible gestures, signifying either rock, paper, or scissors. The winner is determined by the following rules:

1. Paper covers rock paper wins 2. Scissors cut paper scissors win 3. rock breaks scissors rock wins 4. Same gesture draw

Introducing variability in the Introducing variability in the first three phasesfirst three phases

Rock-paper-Scissors Problem: write a program that takes as input the two

players’ gestures and determines who the winning player is, player 1, player 2, or neither. The input should be encoded as follows: 1=rock, 2=paper, 3=scissors. Your program should also ask for how many games to play and then play that many games, keeping track of the number of player 1 wins, player 2 wins, and draws. Print out the over-all results after all games have been played.

Introducing variability in the Introducing variability in the first three phasesfirst three phases

The “Rules” Characterization The “Payoff Matrix” Characterization etc.

Introducing variability in the Introducing variability in the 1st1st phase phase

The “Rules” Characterization 1. If the two gesture are paper and rock, THEN

the winning gesture is paper. 2. If the two gesture are scissors and paper,

THEN the winning gesture is scissors. 3. If the two gesture are rock and scissors , THEN

the winning gesture is rock. 4. If the two gesture are the same, THEN neither

gesture wins.


Encoded Rules 1. If the two gesture are 2 and 1, THEN 2 wins. 2. If the two gesture are 3 and 2, THEN 3 wins. 3. If the two gesture are 1 and 3, THEN 1 wins. 4. If the two gesture are the same, THEN neither

gesture wins.


Object: Gesture 1 = rock is the gesture 2 = paper is the gesture 3 = scissors is the gesture

Object: Winning-gesture 0 = neither gesture wins 1 = rock is winning gesture 2 = paper is winning gesture 3 = scissors is winning gesture


The “Payoff Matrix” Characterization


Draw Player 2 wins Player 1 wins

Player 1 wins

Player 1 wins DrawPlayer 2 wins

Draw Player 2 wins

rock paper scissors

rock

paper

scissors

Player 2

Player 1

The “Payoff Matrix” Characterization


0 2 1

1

1 02

0 2

1 2 3

1

2

3

Player 2

Player 1

Object: Winning-player 0 = neither player wins 1 = player 1 is the winning player 2 = player 2 is the winning player


The “Rules” Characterization selection plan

The “Payoff Matrix” Characterization formula plan winning-player := (gesture1 - gesture2 + 3) mod 3;


Even a novice who knows how to generate alternate alternative characterizations might stop after generating the first unless they are explicitly instructed.

The alternative characterization might lead to a “worse” solution, but even then it would be an opportunity for the novices to improve their plan evaluation and differentiation skills.

Generating alternative characterizations puts the student in a position to make informed judgements in identifying the advantages and disadvantages of alternative plans.


For instance: The payoff matrix characterization leads to a

formula plan that is very concise, but may be hard to understand because it is so concise.

The rule characterization leads to a less concise selection plan, but it may be easier to understand because it is similar to our common-sense intuitions about how people actually play the game.


Introducing variability in the Introducing variability in the 2nd 2nd phasesphases

ActivityActivity With regard to the rule characterization of

the RPS problem, generate multiple approaches to problem decomposition (phase 2) and selection and composition of plans (phase 3) to solve the problem.

Introducing variability in the Introducing variability in the 2nd and 3rd2nd and 3rd phases phases

learning difficulties in computer programming by dr sc li

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