Algorithmic Thinking: Creating Step-by-Step Solutions

This lesson covers algorithmic thinking, a core component of computational thinking as required by OCR J277 Section 2.1. Algorithmic thinking is about designing clear, logical, step-by-step solutions to problems.

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What Is an Algorithm?

An algorithm is a precise, step-by-step set of instructions for solving a problem or completing a task. An algorithm must be:

Property	Description
Finite	It must have a definite end — it cannot run forever
Precise	Each step must be clearly defined and unambiguous
Effective	Each step must be achievable (it can actually be carried out)
Ordered	The steps must be in the correct sequence

Everyday Algorithms

Algorithms are not just for computers — we use them in everyday life:

Task	Algorithm
Making tea	1. Boil water. 2. Put tea bag in cup. 3. Pour water into cup. 4. Wait 3 minutes. 5. Remove tea bag. 6. Add milk if desired.
Getting dressed	1. Choose clothes. 2. Put on underwear. 3. Put on shirt. 4. Put on trousers. 5. Put on socks. 6. Put on shoes.
Crossing the road	1. Stop at the kerb. 2. Look left. 3. Look right. 4. Look left again. 5. If road is clear, cross. 6. Otherwise, wait and repeat.

OCR Exam Tip: An algorithm is NOT a program. An algorithm is the plan (language-independent). A program is the implementation of an algorithm in a specific programming language. You can express an algorithm in English, pseudocode, or a flowchart.

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What Is Algorithmic Thinking?

Algorithmic thinking is the ability to define clear, step-by-step instructions for solving a problem. It involves:

1. Identifying the problem — What needs to be solved?
2. Planning the steps — What sequence of actions will solve the problem?
3. Considering edge cases — What happens with unusual or extreme inputs?
4. Ensuring correctness — Will the algorithm always produce the right output?
5. Optimising — Can the solution be made more efficient?

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Representing Algorithms

Algorithms can be represented in three main ways:

Method	Description	When Used
Written description	Plain English steps	Initial planning, explaining to non-technical people
Pseudocode	Structured, code-like language that is not tied to any programming language	Detailed design, OCR exam questions
Flowcharts	Visual diagrams using standard symbols	Visual learners, design documentation, OCR exam questions

We will cover pseudocode and flowcharts in detail in later lessons.

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Key Algorithmic Concepts

Sequence

Sequence means executing instructions one after another in order.

Step 1: Input the first number
Step 2: Input the second number
Step 3: Add the two numbers together
Step 4: Output the result

Selection (Decision Making)

Selection means choosing which instructions to execute based on a condition.

Step 1: Input the temperature
Step 2: IF temperature > 30 THEN
Step 3:     Output "It is hot"
Step 4: ELSE
Step 5:     Output "It is not hot"
Step 6: ENDIF

Iteration (Repetition / Loops)