B1.1.4 Trace flowcharts for a range of programming algorithms.
• Use of standard flowchart symbols to depict processes, decisions and flows of control
• Standard flowchart symbols: Connector, Decision, Flowline, Input/Output, Process/Operation, Start/End
• Flowcharts for execution flow, to track changes in variables and to determine output
The Big Idea
Flowcharts are visual tools used in computer science to represent the logic and control flow of an algorithm. Tracing a flowchart means following the steps of the algorithm—step by step—to determine how the logic executes, how variables change, and what output is produced. This helps students understand how algorithms behave without having to write code.
Standard Flowchart Symbols
To trace or construct a flowchart accurately, one must use and interpret the standardized symbols:
| Symbol | Name | Function |
|---|---|---|
| ● Oval | Start / End | Represents the start or termination of the flowchart |
| ▭ Rectangle | Process | Denotes a processing step (e.g., calculations or assignments) |
| ◆ Diamond | Decision | Indicates a decision point (e.g., if conditions) |
| ⬒ Parallelogram | Input/Output | Represents user input or output display |
| ○ Circle | Connector | Used to connect sections of a flowchart on the same or different pages |
| → Arrow | Flowline | Shows the direction of flow from one step to another |
Tracing a Flowchart
To trace a flowchart, follow the arrows (flowlines), update variables at each process step, and make decisions at conditional branches.
Example Flowchart (Pseudocode Description):
- Start
- Input a number
- If number is even → Print "Even"
- Else → Print "Odd"
- End
Trace:
- Suppose user inputs
7 - Step 3: Is 7 even? → No
- Go to Step 4: Output "Odd"
- End
Execution Flow and Variable Tracking
Flowcharts are especially useful for:
- Tracking changes in variables: E.g., updating a counter in a loop.
- Understanding execution order: E.g., when conditionals are nested.
- Debugging logic: E.g., locating errors in loops or decisions.
Student-Relatable Example
Scenario: You're making a quiz app.
A simplified flowchart might:
- Start
- Ask a question
- Get user answer
- Compare to correct answer
- If correct, increase score
- Repeat for next question
- End and show score
By tracing this flowchart:
- You monitor how the score variable changes with each question.
- You check that the loop terminates after a set number of questions.
- You ensure correct and incorrect answers are handled properly.
Conclusion
Tracing flowcharts reinforces algorithmic thinking by making execution logic visible and concrete. Mastery of this skill enables students to predict output, understand algorithm behavior, and verify program correctness—essential abilities in both programming and debugging.