An algorithm is a precise, step-by-step set of instructions to solve a problem or accomplish a task. A good algorithm is: correct, unambiguous, finite (has an end), and efficient.
Algorithms can be represented using pseudocode — an informal, language-independent description of logic
Or flowcharts — visual diagrams showing each step and decision
Pseudocode is closer to actual code; flowcharts are easier to visualise for beginners
Flowchart Symbols
Standard Shapes and Meanings
Shape
Meaning
Oval / Rounded rectangle
Start / End (terminator)
Rectangle
Process (action or calculation)
Diamond
Decision (Yes/No question)
Parallelogram
Input / Output
Arrow
Flow of control
Exam tip:Edexcel may ask you to draw or complete flowcharts — know your symbols!
Pseudocode Conventions
Edexcel Pseudocode Style
name ← INPUT("Enter your name")
IF name = "Admin" THEN
OUTPUT "Welcome, Admin!"
ELSE
OUTPUT "Access denied"
END IF
FOR i ← 1 TO 5
OUTPUT i
END FOR
Assignment uses ← (left arrow)
Conditions use IF/THEN/ELSE/END IF; loops use FOR/END FOR and WHILE/END WHILE
Exam Practice
Have a go at this question
Edexcel-style question
Write an algorithm in pseudocode that asks the user to input a number and outputs whether it is positive, negative, or zero.
4 marks
num ← INPUT("Enter a number") IF num > 0 THEN OUTPUT "Positive" ELSE IF num < 0 THEN OUTPUT "Negative" ELSE OUTPUT "Zero" END IF
Key Takeaways
What to Remember
Algorithm = precise, finite, unambiguous steps to solve a problem
Pseudocode: uses ←, IF/THEN/ELSE/END IF, FOR/END FOR, WHILE/END WHILE