1.1 · Defining a Problem (IPO Analysis)

Goal: transform a fuzzy problem statement into a clear list of Inputs, Processes and Outputs.

What IPO means

Input → Process → Output. Every programming task can be modelled this way.

┌────────┐    ┌────────┐    ┌────────┐
│ Input  │ ──▶│Process │ ──▶│ Output │
└────────┘    └────────┘    └────────┘

Before writing a single line of code, fill in all three boxes.

Why it matters

Skipping IPO leads to:

• Programs that ignore important inputs.
• Forgotten outputs (e.g. logs).
• Solutions that solve the wrong problem.

Worked example · BMI calculator

Field	Content
Input	weight in kg (float), height in metres (float)
Process	bmi = weight / (height × height); classify into Underweight/Normal/Overweight/Obese
Output	bmi (one decimal); category text

IPO template

Problem name : 
Author       : 
Date         :

INPUTS
  - name : type : example
  - …

PROCESSES
  - step 1 …
  - step 2 …
  - …

OUTPUTS
  - name : type : example
  - …

ASSUMPTIONS
  - …

VALIDATIONS
  - …

Fill the template in 5 minutes before coding. Most marks lost in SBA come from missing this step.

Defining problem scope

Always state explicitly what is and what is not in scope.

Scope: the program computes BMI for a single user at one time.
Out of scope: storing historical BMI, multi-user accounts, ideal weight calculation.

Scope keeps the project finishable.

Exam-style question

Q (4 marks): A teacher wants a program that takes a class's exam marks and prints the highest mark, lowest mark and average. Carry out an IPO analysis.

Sample answer:

• Inputs: a list of integer marks (e.g. [78, 65, 90, 55, 82]).
• Processes: validate that all marks are 0–100; find max and min; compute average = sum / count.
• Outputs: highest mark, lowest mark, average (rounded to 1 decimal place).

Key takeaways

• IPO before code.
• Scope decisions prevent feature creep.

➡️ Next: 1.2 Decomposition