Module 1.7 Software
Develop e t
Ca bridge Lower Seco dary
Co puti g 3 Grade 8
Based on book by Victoria Ellis & Sarah Lawrey
Teacher: Aditya Shirke
Lear i g Objective
Deco po itio
Algorit
A aly i
Te ti g
Understand what decomposition is and
Learn to predict algorithm outcomes
Create test plans using different types
why it's used in programming
and test predictions
of data
Learn how to decompose problems into
Understand iterative development in
Understand why various data types are
sub-problems
programming
needed for testing
By the end of this module, you'll understand key software development concepts and practices used by professional programmers.
W at i Deco po itio ?
Definition: Breaking down large problems into smaller, manageable
parts
Sub-problems: Small problems that combine to solve a larger
overall problem
Key Point: It's easier to solve many small sub-problems than one
large problem
Analogy: Like decomposing organic material into compost breaking down into smaller parts
Decomposition is a fundamental concept in computing that helps us tackle complex problems by dividing them into simpler components.
No -Progra
i g Exa ple: I truder Alar
Sy te
Problem: Design an intruder alarm system
Set Alar
C eck for I truder
Tur Alar
Configure the system to detect
Monitor sensors to detect any
Disable the alarm when authorized access
unauthorized entry
unauthorized presence
is confirmed
Note: Sub-problems can be broken down into steps, but steps cannot be broken down further.
Off
No -Progra
Sc ool
i g Exa ple: Getti g Ready for
Problem: Help Sofia remember her morning routine
1
Getti g Up
Wake up when alarm rings, get out of bed
2
Getti g Wa
ed
Brush teeth, wash face, shower
3
Getti g Dre
ed
Put on school uniform or appropriate clothes
4
Havi g Breakfa t
Eat a nutritious meal to start the day
5
Packi g Bag
Gather books, homework, and supplies
Key Feature: Sub-problems are independent and reusable
Progra
i g Exa ple: S ake a d Ladder Ga e
Problem: Create a computer game of snakes and ladders
Deco po itio Exa ple 1:
01
02
03
Loading and starting a new game
Player making a move
Moving the piece
04
05
Checking if on snake/ladder and moving
Checking if player has won
Alter ative Deco po itio : Sa e Proble , Differe t
Approac
Deco po itio Exa ple 2:
01
02
Select number of players
Set players in first position
03
04
Display board
Roll number block
05
06
Move player
Check if they have won
Key Insight: Multiple valid ways to decompose the same problem. There is no single "correct" way to break down a problem - different
approaches can all lead to successful solutions.
W y Do We Deco po e Proble
?
Hu a Nature
Tea
Collaboratio
Specializatio
Breaking large tasks into smaller ones
Multiple programmers can work on
Different programmers can focus on
is more natural for our brains to
different sub-problems
their expertise areas
process
simultaneously
Efficie cy
Reu ability
Faster development when work is
Sub-routines can be reused multiple
divided
times
W at i Iterative Develop e t?
Definition: Writing programs in stages, testing each part before
moving to the next
Process: Write
Repeat
³ Test ³ Change/Fix ³ Write Next Part ³ Test ³
Key Principle: Don't write all code first and then test everything at
once
Benefit: Easier to find and fix problems in smaller code sections
Iterative development is like building a house brick by brick, checking each layer is solid before adding the next, rather than building the whole
house and then checking if it's stable.
Iterative Develop e t Proce
Exa ple: Fire, Water, Eart ga e
³ Test
Step 2: Write code for first player choice ³ Test
Step 1: Write code for player names input
Step 3: Continue building and testing each part
Advantage: Problems are caught early and are easier to fix
Predicti g Outco e
Definition: Guessing what will happen when a program runs
Process:
1. Read the algorithm carefully
2. Think about expected outputs with specific inputs
3. Run the program to check if prediction was correct
Focus: Get an overview of the program, not every detail
Goal: Identify what the outcomes will be (outputs or data changes)
Type of Te t Data
Nor al Te t Data
I valid Te t Data
Bou dary Te t Data
Data that is accepted or within bounds
Data that is not accepted or outside
Data on the edge of what is/isn't allowed
bounds
Example for age
Example for age
f16: 10, 12, 15
Example for age
f16: 17, 20, 25
Why All Types? Ensures program works correctly in all situations, not just the expected ones.
f16: 16, 17
Te t Pla Creatio
Purpose: Systematic approach to testing programs
Test data type
Description
Example inputs
Expected output
Actual result
Normal
Within acceptable
12
"Welcome to the club!"
To be filled
20
"Sorry, you're too old"
To be filled
16
"Welcome to the club!"
To be filled
range
Invalid
Outside acceptable
range
Boundary
At the edge of
acceptance
Steps: Create table
³ Add normal data ³ Add invalid data ³ Add boundary data
Exa ple: Te ti g Age Progra
Program Rule: Club allows children 16
or younger to join
Boundary Testing Reveals:
Original Code Condition: if (age < 16)
A 16-year-old should be
Problem Found: Original condition
original code would reject
excludes 16-year-olds
allowed to join, but the
them!
Solution: Change to if (age <= 16)
Lesson: Boundary testing reveals
edge case errors
Key Point: Test with range of data,
not just one or two values
Su
ary
Key Takeaway
Deco po itio
Iterative Develop e t
Break large problems into
Write and test code in small stages
manageable sub-problems
Multiple valid approaches to
Fix problems early before they
compound
decomposition exist
Predictio
Te ti g
Think through program logic before running
Use normal, invalid, and boundary test data
Real-World Application: These practices are essential in professional software
development and will help you create more reliable, efficient programs.