1.2a Representing Algorithms: Flowcharts & Pseudocode — Edexcel 1CP2

Representing Algorithms

An algorithm can be represented in different ways before being coded. The two most common on the Edexcel 1CP2 specification are flowcharts and pseudocode. Both allow you to plan and communicate a solution without worrying about the exact syntax of a programming language.

Flowcharts

A flowchart uses standard symbols connected by arrows to show the flow of an algorithm.

Symbol	Shape	Meaning
Terminal	Rounded rectangle / oval	Start or End of the algorithm
Process	Rectangle	An action or calculation (e.g. total = total + score)
Decision	Diamond	A yes/no question or condition (e.g. is score > 50?)
Input/Output	Parallelogram	Data is entered or displayed
Flow line	Arrow	Shows the direction/sequence of steps

Flowcharts are useful for visualising the logic of an algorithm, especially when there are decision points (branches) or loops.

Exam tip: In the Edexcel exam, you must use the correct symbols. A diamond is always a decision; a rectangle is always a process. Confusing these will cost marks.

Pseudocode — Edexcel Style

Pseudocode is structured like code but uses plain English. The Edexcel 1CP2 specification uses the following conventions:

Construct	Edexcel Pseudocode Syntax
Input	`INPUT variableName`
Output	`OUTPUT variableName` or `OUTPUT "text"`
Assignment	`variableName <- value`
If statement	`IF condition THEN ... ELSE ... ENDIF`
Count-controlled loop	`FOR i <- 1 TO 10 ... NEXT i`
Condition-controlled loop	`WHILE condition DO ... ENDWHILE`
Procedure call	`CALL procedureName()`

Example — check if a number is even or odd:

INPUT num
IF num MOD 2 = 0 THEN
  OUTPUT "Even"
ELSE
  OUTPUT "Odd"
ENDIF

Exam tip — Edexcel pseudocode: Edexcel does not require strict, formal pseudocode syntax. Examiners accept clearly structured, readable pseudocode provided the logic is unambiguous. You will not lose marks for using slightly different keywords (e.g. PRINT instead of OUTPUT) as long as the intent is clear. The conventions shown above are recommended as they match Edexcel's mark scheme examples.

Comparing Flowcharts and Pseudocode

Aspect	Flowchart	Pseudocode
Visual?	Yes — shapes and arrows	No — text-based
Good for	Visualising flow, decision branches	Showing exact logic and syntax
Easy to convert to code?	Less direct	Very direct — close to real code
Used when	Explaining to non-programmers	Planning code, sharing with developers

⚠️ Common Mistakes

Using a rectangle for a decision instead of a diamond
Forgetting ENDIF or ENDWHILE in pseudocode — every block must be closed
Not using arrows in flowcharts — you must show direction of flow
Writing pseudocode in a specific programming language syntax — it should be language-independent
Forgetting to include START and END terminals in a flowchart

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Key points covered in this video

Standard flowchart symbols and when to use each
Drawing flowcharts for sequence, selection, and iteration
Edexcel pseudocode notation and conventions
Converting between flowcharts, pseudocode, and Python
Exam question strategies for algorithm representation

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Worksheet — 1.2a Flowcharts & Pseudocode

8 Edexcel-style questions · 20 marks · instantly marked

Q1State the flowchart symbol used to represent a decision.[1 mark]

✅ Mark scheme

Mark scheme

Diamond shape. [1 mark]

Q2State the flowchart symbol used to represent a process (action or calculation).[1 mark]

✅ Mark scheme

Mark scheme

Rectangle. [1 mark]

Q3Write the Edexcel pseudocode to input a number called "score", then output "Pass" if it is 50 or above, otherwise output "Fail".[3 marks]

✅ Mark scheme

Mark scheme

INPUT score [1]
IF score >= 50 THEN [1]
OUTPUT "Pass"
ELSE
OUTPUT "Fail"
ENDIF [1 — must close the block]

Q4Give one advantage of using a flowchart over pseudocode to represent an algorithm.[1 mark]

✅ Mark scheme

Mark scheme (any 1)

Easier to follow visually [1] / Can be understood by non-programmers [1] / Logic/flow is easier to see [1]

Q5Write pseudocode using a FOR loop to output the numbers 1 to 10.[2 marks]

✅ Mark scheme

Mark scheme

FOR i <- 1 TO 10 [1]
OUTPUT i
NEXT i [1]

Q6Write pseudocode using a WHILE loop to keep asking for a password until the user enters "secure123".[3 marks]

✅ Mark scheme

Mark scheme

INPUT password [1]
WHILE password != "secure123" DO [1]
INPUT password
ENDWHILE [1]
(Accept any valid logical equivalent)

Q7Explain why pseudocode is preferred over a specific programming language when designing an algorithm.[2 marks]

✅ Mark scheme

Mark scheme

Pseudocode is not tied to any specific language [1]; this means any programmer can read and implement it in their preferred language, and it focuses on the logic rather than syntax [1].

Q8Describe the purpose of an arrow (flow line) in a flowchart and explain what happens at a diamond symbol.[3 marks]

✅ Mark scheme

Mark scheme

An arrow shows the direction/sequence in which steps are executed [1]. A diamond represents a decision/question [1]; it always has two or more exit paths (typically Yes/No or True/False) which direct the algorithm to different branches [1].

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Representing Algorithms

Flowcharts

Pseudocode — Edexcel Style

Comparing Flowcharts and Pseudocode

Key points covered in this video

Worksheet — 1.2a Flowcharts & Pseudocode

Mini Test — 1.2a Flowcharts & Pseudocode

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