Producing Algorithms with Pseudocode and Flow Diagrams

Overview

• Importance of creating, interpreting, correcting, and refining algorithms.
• Difference in approach based on exam papers:
  • Paper 1: Theoretical approach using pseudocode and flowcharts.
  • Paper 2: Practical coding using Python on a computer.

Flow Diagrams

• A flow diagram (or flowchart) represents algorithm steps visually.
• Example process:
  • Start at the top.
  • Input two numbers.
  • Compare numbers and follow different branches based on conditions.
  • Output results and stop.

Pseudocode

• Acts as an intermediary between plain English and actual code.
• Allows representation of algorithms without strict syntax.
• Example:
  • Inputs two numbers.
  • If statement to compare numbers and print the larger one.

Refinement of Algorithms

• Exams may require refining existing algorithms.
• Example task: Modify an algorithm to process three numbers instead of two.
  • Identify and adjust input sections.
  • Adjust decision-making logic in flow diagrams.

Example Algorithms

• Nitrate Level Algorithm:
  • Determines carbon dosing in fish tanks based on nitrate levels.
  • Flow diagram steps: Input nitrate level, series of conditions to decide dosing.
  • Equivalent pseudocode provided.

Common Flow Diagram Symbols

• Terminal Symbol: Represents start/end of a process.
• Process Symbol: Represents initialization, processing, or calculations.
• Decision Symbol: Represents a decision point with yes/no, true/false outcomes.
• Input/Output Symbol: Represents data input and output.
• Subroutine Call Symbol: Represents calls to subroutines within the main program.
• Line with Arrow: Represents control flow between shapes.

Key Takeaways

• Skills in pseudocode and flow diagrams are crucial for theoretical exams.
• Understanding different representations of the same algorithm.
• Familiarity with flowchart symbols is essential for exams.