Algorithms in pseudocode/flowcharts

A Systematic Approach to Problem Solving

Before writing any code, a good programmer follows a structured series of steps. This systematic approach ensures the problem is fully understood before any solution is attempted, reducing errors and wasted effort.

  1. Understand the problem - read carefully and identify exactly what needs to be solved.
  2. Identify inputs and outputs - what data goes in, and what result must come out?
  3. Design the algorithm - plan the step-by-step logic before writing any code.
  4. Represent the algorithm - write it as pseudocode, a flowchart, or program code.
  5. Test the solution - trace through the algorithm with example data to verify it works correctly.

This process separates thinking from typing - designing the algorithm properly first makes the programming stage much more straightforward.

Three Ways to Represent an Algorithm

AQA requires algorithms to be represented in three forms: pseudocode, flowcharts, and program code. Each form serves a different purpose but describes the same underlying logic. The example below uses a simple problem - "ask the user for a number, then output double that number" - to show all three representations.

Pseudocode uses structured English-like keywords to describe an algorithm without worrying about any specific programming language. AQA uses a standard pseudocode format - keywords such as INPUT, OUTPUT, and the assignment arrow ← are always written the same way.

INPUT number
result ← number * 2
OUTPUT result

This pseudocode is language-neutral - it could be implemented in Python, C#, VB.NET, or any other language without changing the logic.

Flowcharts represent an algorithm visually using standard symbols connected by arrows. Each symbol has a specific meaning:

  • Oval - Start or End
  • Parallelogram - Input or Output
  • Rectangle - Process (e.g. a calculation)
  • Diamond - Decision (a yes/no question)

Program code is the implementation of the algorithm in a real programming language. The logic is identical to the pseudocode - only the syntax changes. AQA supports Python, VB.NET, and C#.

The same algorithm implemented in Python:

number = int(input())
result = number * 2
print(result)

Notice that the three lines of pseudocode map directly to three lines of program code. This is the value of designing in pseudocode first.

 Key Takeaways

  • A systematic approach means understanding the problem and designing an algorithm before writing any code.
  • Always identify inputs and outputs as the first step in algorithm design.
  • Pseudocode uses structured English-like keywords and is language-neutral - AQA uses a standard format.
  • Flowcharts represent the same logic visually, using standard symbols (oval, rectangle, parallelogram, diamond).
  • Program code is the implementation of the algorithm in a real language - the logic should match the pseudocode exactly.
  • All three representations describe the same underlying algorithm - only the notation differs.