📘 Unit 6 (9.

6) – Full Revision Notes

🧩 1. Writing Python Code from a Flowchart
🔹 Definition:
A flowchart visually represents a program’s steps using symbols.

🔧 How to Use:
●​ Oval: Start/End → e.g. Start​

●​ Rectangle: Process → e.g. x = 5​

●​ Diamond: Decision → e.g. if x > 10:​

●​ Arrow: Control flow (direction of execution)​

🖥️ Python Example:
python
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x = 10
if x > 5:
print("Big")
else:
print("Small")

❓ Questions:
1.​ What does a diamond represent in a flowchart?​

2.​ Convert this flowchart to code:​

○​ Start → Input number → If even → Print "Even" → Else → Print "Odd"​

🧠 2. Decomposition & Iterative Development
🔹 Definitions:
●​ Decomposition: Splitting problems into smaller tasks.​

●​ Iterative Development: Repeating design, build, and test cycles.​

⚙️ How it Works:
1.​ Break down big problems into parts.​

2.​ Work on each part.​

3.​ Test and refine continuously.​

🖥️ Example:
Building a calculator:

●​ Step 1: Get inputs​

●​ Step 2: Add/subtract/multiply​

●​ Step 3: Output result​

❓ Questions:
1.​ Name 2 benefits of decomposition.​

2.​ Why do programmers use iterative development?​

🔍 3. Binary Search
🔹 Definition:
A method to find a value in a sorted list by repeatedly halving the search area.

🧪 How It Works:
1.​ Check the middle.​

2.​ If match → return.​

3.​ If smaller → search left.​

4.​ If larger → search right.​

🖥️ Example:
List: [3, 6, 9, 12, 15]​
Target: 12​
Middle = 9 → 12 > 9 → move right → found 12.

❓ Questions:
1.​ Why must the list be sorted?​

2.​ Compare binary and linear search.​

🔁 4. Count-Controlled Loop
🔹 Definition:
A loop that repeats a fixed number of times.

🔧 Common Format:
python
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for i in range(5):
print("Hello")

🧪 Trace Table Example:

python
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x = 0
for i in range(3):
x += i

i x

0 0

1 1

2 3

❓ Questions:
1.​ What is the output of for i in range(4): print(i)?​

2.​ What’s the final value of x above?​

🔤 5. Data Types
🔹 Key Types:
●​ int – whole numbers (e.g. 5)​

●​ float – decimals (e.g. 3.14)​

●​ str – text (e.g. "hello")​

●​ bool – true/false​

🖥️ Example:
python
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name = "Max"
age = 16
height = 1.75
enrolled = True
❓ Questions:
1.​ What type is "123"?​

2.​ Which type stores True/False?​

⚠️ 6. Errors in Programming
🔹 Types:
●​ Syntax Error: Code violates Python grammar​

●​ Logic Error: Runs but gives wrong results​

●​ Runtime Error: Fails during execution​

🧪 Debugging:
●​ Use print() to trace.​

●​ Read error messages carefully.​

●​ Test parts of your code in chunks.​

🖥️ Example:
python
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x = int(input("Enter a number: "))
print(10 / x) # Crashes if x = 0

❓ Questions:
1.​ What kind of error happens if print("hi)?​
 2.​ How do you debug a runtime error?​

📋 7. Writing a Test Plan

🔹 Definition:
A document showing how a program is tested, including inputs, expected results, and
outcomes.

🧪 Example Table:
Tes Description Input Expecte Actual Pass
t d ?

1 Valid number 5 25 25 ✅
2 Zero test 0 Error Error ✅
❓ Questions:
1.​ Why is a test plan important?​

2.​ What sections are in a test table?​

📘 Computing – Unit 9.6 Detailed Revision

Notes

1. Writing Python Code from a Flowchart

🧠 What is a Flowchart?
●​ A flowchart visually represents a process or algorithm using different shapes and
arrows.​
 ●​ Each shape has a specific meaning:​

○​ Oval: Start/End of the program.​

○​ Rectangle: Instruction/Process (e.g., x = 5)​

○​ Diamond: Decision/Condition (e.g., if x > 10)​

○​ Arrows: Show the flow from one step to another.​

💡 Example Flowchart:
css

Sao chépChỉnh sửa

[Start] → [x = 10] → [x > 5?] → Yes: print("Big") | No: print("Small")

🐍 Python Code Equivalent:

python

Sao chépChỉnh sửa

x = 10

if x > 5:

print("Big")

else:

print("Small")

🔁 Practice Tip:
When given a flowchart, identify:

1.​ Input/Start​
 2.​ Sequence of processes​

3.​ Decision branches​

4.​ Output​

2. Decomposition & Iterative Development

🧩 Decomposition
●​ Breaking down a big problem into smaller, manageable parts (modules or functions).​

●​ Makes code easier to write, test, and debug.​

🔁 Iterative Development
●​ Building a system step-by-step.​

●​ Each version is improved by:​

1.​ Testing​

2.​ Fixing errors​

3.​ Enhancing features​

🧮 Example: Calculator App

●​ Decomposition:​

○​ Input function​

○​ Calculation function​

○​ Output display​

●​ Iteration: Test each part → improve if it fails → test again.​

3. Binary Search
🔍 What is Binary Search?
●​ A fast algorithm to search for an item in a sorted list.​

●​ Time Complexity: O(log n)​

🔁 How It Works:
1.​ Find the middle of the list.​

2.​ If it's the target → found.​

3.​ If the target is smaller → search the left half.​

4.​ If larger → search the right half.​

📦 Example:
python

Sao chépChỉnh sửa

list = [2, 4, 6, 8, 10]

target = 8

●​ Step 1: Middle = 6 → 8 > 6 → go right.​

●​ Step 2: Middle = 8 → FOUND!​

⚠️ Important:
●​ List must be sorted before using binary search.​
4. Count-Controlled Loops & Trace Tables
🔁 Count-Controlled Loop
●​ A loop that runs a fixed number of times.​

●​ Syntax:​

python

Sao chépChỉnh sửa

for i in range(3):

print(i)

●​ Output:​

Sao chépChỉnh sửa

🧮 Trace Table
●​ A tool used to track how variables change during loop execution.​

●​ Useful for debugging and understanding logic.​

i
 0

5. Data Types in Programming

🧠 Common Data Types:
Type Description Example

int Integer (whole number) 3, 100

float Decimal number 3.14,

1.5

str String/Text "hello

"

bool Boolean (True/False) True

✅ Example:
python

Sao chépChỉnh sửa

name = "Alice" # str

age = 17 # int

gpa = 3.75 # float

active = True # bool

⚠️ Why Important?
●​ Using correct types prevents bugs and improves program efficiency.​

6. Types of Programming Errors

Type Description Example

Syntax Error Breaking language rules if x = 5 → should be ==

Logic Error Code runs but gives wrong if x > y: return x*y instead
result of x+y

Runtime Error Code crashes when it runs print(5 / 0) → Division by 0

🧰 Debugging Techniques:
●​ Use print() to check variable values.​

●​ Read error messages carefully.​

●​ Create and run multiple test cases.​

7. Writing a Test Plan
📝 What is a Test Plan?
●​ A table used to ensure that a program behaves as expected with different inputs.​

📊 Structure:
Test Description Input Expecte Actual Pass/Fai
# d l

1 Add 5 and 3 5+3 8 8 Pass

2 Divide by zero 10 / 0 Error Crash Fail

💭 Why Test Invalid Inputs?

●​ To ensure the program can handle errors without crashing.​

8. Trace Tables and Iteration

●​ Trace tables help track values across iterations, especially in loops.​

●​ They’re vital for spotting logic errors.​

🧪 Example:
Problem: If x >= y, add them. Else, multiply.

python

Sao chépChỉnh sửa

x = 4
y = 3

if x > y:

result = x * y # ❌ Should be x + y
●​ Logic Error: Condition is true, but it multiplies instead of adding.​

9. Online User Data & Big Data

🌐 How Data is Collected:
●​ Web tracking: pages visited, forms filled.​

●​ Shopping behaviour: products viewed/purchased.​

●​ Social Media: posts liked, location, keywords.​

💸 Why is it Valuable?
●​ Helps companies target ads, understand customer interests, and improve sales.​

💾 Big Data: 5 V’s

V Meaning

Volume Massive amounts of data

Velocity Speed of data generation

Variety Different types: video, text, numbers

Veracity Data accuracy and reliability

Value Usefulness of data to make

decisions