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Program Development
Goals • Understand an example of program
development• Understand the characteristics of a
good algorithm• Understand how algorithmic patterns
can help design programs
1.1 Program Development
Program development can be defined in three steps:• Analysis: Understand the problem• Design: Organize the solution• Implementation: Get the solution running
Program development is the progression from analysis to design to implementation
Analysis
Synonyms for analysis• inquiry, examination, study
Activities• Read and understand the problem
statement• Determine test cases
Test Cases
A program to compute your weighted average
Course Grade from our syllabus
15% Labs35% Projects15% Test 115% Test 220% Final
Determine three test cases:Labs Projects
Test 1 Test 2 Final Average
Design
Synonyms of design: model, think, plan, devise, pattern, propose, outline
We'll use these design tools:• algorithms• algorithmic patterns• algorithm walkthroughs
Algorithms
An algorithm is a set of activities that solves a problem
An algorithm must:• list activities that must be performed• list the activities in the proper order
Algorithm to Bake a Cake
A recipe (a.k.a. an algorithm)• Preheat Oven• Grease Pan• Mix ingredients• Place ingredients into pan• place pan in oven• remove pan after 35 minutes
Switch some activities around ... what happens if …
Algorithmic Patterns
Pattern: Anything shaped or designed to serve as a model or guide in making something else.
Algorithmic Pattern: • Serves as a guide to help develop programs • It represents a common type of action that
occurs over and over again in programs• A solution that can be used different
contexts The Input/Process/Output (IPO)
Pattern can be used.• This IPO pattern will be used in our second
lab and our first project and quite often in the future
IPO Algorithmic Pattern
Pattern: Input/Process/Output (IPO)Problem: The program requires input
datato generate the desired
informationOutline: 1. obtain input data from user
2. process input data3. output the results
Patterns ala Alexander
"Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice."
From A Pattern Language, Christopher Alexander, Oxford University Press, 1977
Example of Algorithm Design
The design deliverable will be an algorithm
The IPO patterns provides a guide to design a more specific algorithm :
IPO Model IPO applied to Chapter 1 Case Study
I)nput Obtain the items that count for 127A
P)rocess Compute the course grade O)utput Display the course grade
Refining Activities in algorithms
We often need to refine one or more activities (algorithm steps). • For example, Compute the course grade
might now be refined with the mathematical addition + and multiplication * symbols
Implementation
Synonyms for Implementation• accomplishment, making good, execution
Implementation deliverable: computer program
Let's do it
We'll use the programming language Java
We'll use the Eclipse Development Environment