Queensland University of Technology CRICOS No. 00213J 1 ITB001 Problem Solving and Programming Lecture 1 Faculty of Information Technology Queensland University

Queensland University of TechnologyCRICOS No. 00213J

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ITB001Problem Solving and Programming

Lecture 1

Faculty of Information Technology

Queensland University of Technology

CRICOS No. 00213J

a university for the worldrealR 2

Meet the staff

• Dr. Glenn Smith

• Coordinator• Margaret Street office

• Prof. Colin Fidge

• Lecturer• S Block office

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Format

• Contact time:– 1 x 1-hour lecture each week– 1 x 2-hour workshop each week– ‘Drop in’ practical sessions each week

• Preparation:– Must read lecture notes and listen to pre-recorded

topics before attending lecture

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Assessment

• A major assignment, in three parts (50% Total)• Written examination (50%)

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Software

• In this unit we use a software package called DrScheme• DrScheme is available in the computer laboratories• You may download your own copy of DrScheme from http://www.drscheme.org/

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Reference material

• DrScheme has a built-in ‘help desk’ with lots of information

• Relevant textbooks:– Concrete Abstractions: An Introduction to Computer

Science Using Scheme, by M. Hailperin, B. Kaiser and K. Knight•http://www.gustavus.edu/+max/concrete-abstractions.html

– Structure and Interpretation of Computer Programs, by H. Abelson and G. Sussman with J. Sussman•http://mitpress.mit.edu/sicp/

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Reference material

– The Schematics of Computation by V. Manis and J. Little (Prentice-Hall, 1995)

– How to Design Programs: An Introduction to Programming and Computing, by M. Felleisen, R. Findler, M. Flatt and S. Krishnamurthi (MIT Press 2002)

• The first two textbooks listed above are available at the QUT bookshop, as well as online

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More information

• Lecture notes, assignment sheets, exercise solutions, etc, will be available from the ITB001 web site– Check this web site regularly– Read the Course Unit Outline and the Week One Unit

Information

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What is this unit about?

• Problem solving skills and strategies used in software development– Decomposing big problems into manageable parts– Using abstraction to make solutions readable and

maintainable• An understanding of fundamental programming skills

– Generic coding techniques applicable to a wide range of programming and scripting languages

– Familiarity with the factors that affect the performance of computer programs

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Teaching format

1. Each week’s lecture will introduce a programming concept that can be used to solve particular computational problems

2. In the workshops you will then have an opportunity to use this concept to solve several example problems, with help from your classmates and tutors

3. Finally, the practical sessions will give you an opportunity to check your solutions on the computer (or you can use your own computer)

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Brush up on your maths

• In exercises and the assignment we will assume knowledge of some mathematical concepts such as rational numbers, modulo arithmetic, Boolean logic, etc

• We won’t have time to go through these topics in detail during lectures, so you will need to revise some of them yourselves as homework

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Aims of today’s lecture

• Introduce different approaches to problem solving• Identify the relationship between problem solving and

programming• Explain the role of computer programming in developing

software systems• Introduce a sequence of steps used to develop a

computer program• Introduce some of the terms and concepts used in

computer programming


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Problem Solving and Programming

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Problem solving strategies

• Trial and error– In trial and error, we try an option to see if it works– If it works, then we have a solution– If it doesn’t work—or there is an error—then we try

another option • Brainstorming

– An organized approach for producing ideas by letting the mind think without interruption

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• Lateral thinking– A technique of problem solving by approaching

problems indirectly at diverse angles instead of concentrating on one approach at length

• Divide and conquer– A strategy particularly related to programming– Identify sub-parts of the problem that are easier to

solve, then recombine individual solutions to produce an overall solution

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• Decrease and conquer– A variation on divide and conquer where the problem

itself cannot be decomposed– Decrease the size of the set of values involved,

typically by one, and repeat this process until the solution is trivial

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• Other useful strategies:– Clarify the problem– Identify key elements– Draw a diagram– Consider a specific

example– Refer to literature

– Consider related problems

– Consider an extreme case

– Discuss with peers

http://www.une.edu.au/psychology/staff/malouff/problem.htm

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Programming

• What is programming?– Computer programming (often simply

programming) is the craft of implementing one or more interrelated abstract algorithms using a particular programming language to produce a concrete computer program. Programming has elements of art, science, mathematics, and engineering.

[Wikipedia]

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Problem solving and programming

• Programming is our tool for realising a particular solution• But we must “solve” the problem first, then design and

build the solution– However, the design must be compatible with the

tools used– Hence we must first understand how to use the tools

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• Problem: Your dog gets wet when it rains

• Solution: A dog house• Design: An enclosed

structure of wood and nails

• Implementation: Needs carpentry skills

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• In programming this means we need to understand:– The programming language used to express our

solutions (the toolkit)– An appropriate programming strategy (how to

assemble the parts)– The computational processes produced by our

programs (properties of the finished program)


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Software Engineering: The Big Picture

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Software engineering

• Software engineering is the discipline of solving a computational problem by building a software system

• Programming is only one part of software engineering• Implementation of large projects can take many years,

involve many people, and cost millions of dollars• Successful completion of large projects requires:

– Project planning and management – Team work – Communication skills– Technical knowledge and skills

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Small-scale programming

• In this unit we will solve small problems and write small programs– We must do this first to develop and practice our

problem solving and programming skills– Other units look at large-scale problem solving

• We must develop a basic knowledge of programming before we can be part of a software engineering team– In the same way a doctor must first learn anatomy

before undertaking clinical diagnosis

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Significance

• Even if you are not a software engineer, all I.T. professionals should understand the programming process:– To communicate effectively with other I.T.

professionals– To appreciate what is practical in the development of

computer programs


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The Programming Process

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Programming processes

• When solving large problems, we must follow a well-defined process to achieve repeatable success

• The process that we will follow in this unit focuses on the problem solving and programming part of the larger software engineering process

• We will apply this process to small problems so that we are confident and competent in the process when we need to work on larger problems

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The traditional ‘waterfall’programming process

Analyse

Design

Implement

Test

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Steps in the programming process

1. Analysis– What information is important?– Is further information or knowledge required?– What values are given as inputs?– What values are required as outputs?– Identify test cases and their answers (otherwise,

how would we know when we’ve finished?)– Identify sub-tasks– Consider initial strategies for solving this problem

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2. Design– Develop the overall solution– Identify useful programming constructs– Identify existing code that may be reused directly or

can provide a model for the required code– May need to go back and further analyse the

problem

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3. Implement– Translate the design into program code– Start with smaller pieces of the design– Write simplified code first, then test it, then extend it

• Do not need to get the complete answer in one step

– Use a checklist to track any possible problems– Combine smaller pieces to produce the complete

solution

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4. Test– Check that the program works correctly– Compare actual outputs with pre-calculated values

or predicted behaviour• Just because it looks right doesn’t mean it is right

– Consider what values might ‘break’ your program• e.g., zero values, empty lists, out-of-range

values, values of the wrong type, repeated values, etc

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Computer programming concepts

• Programming involves many new concepts• What is a computer program?

– An unambiguous set of instructions that tells a computer how to behave in response to given inputs

• How does a program run?– We need to ‘compile’ or ‘interpret’ programs from

human-readable form into machine-executable code– Each of the resulting instructions is evaluated

individually, in sequence

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Computer programming concepts

• What does a program contain?– Identifiers (names)– Variables (named values)– Expressions (something that can be evaluated)– Control constructs (directives to the computer)– Procedures (a named expression that can be reused)

• What are the common tasks involved?– Coding (writing the computer program)– Testing (testing for errors in a program)– Debugging (removing errors, or bugs, from programs)

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What is Scheme?

• Scheme is a ‘functional’ programming language often used for solving problems requiring a lot of searching

• We use it as a teaching language because it is simple yet powerful– The DrScheme programming environment allows us

to develop and execute programs quickly and easily• The principles we will illustrate using Scheme transfer

readily to other programming languages (such as Java and C#) and scripting languages (such as Perl and Python)

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Homework

• Before next week’s workshop, you must complete the worksheet provided on the ITB001 web site

• If you have any difficulties, please discuss with workshop tutors and lab facilitators in week 2

• Ensure that you have allocated yourself to a workshop session

Documents

Queensland University of Technology CRICOS No. 00213J 1 ITB001 Problem Solving and Programming Lecture 1 Faculty of Information Technology Queensland University