Tracing Algorithms (AQA GCSE Computer Science)

Tracing Algorithms

What is a trace table?

• A trace table is used to trace through an algorithm and to test algorithms and programs for logic errors that appear when an algorithm or program executes

• Trace tables can be used with flowcharts, pseudocode or program code

• A trace table can be used to:

  • Discover the purpose of an algorithm by showing output data and intermediary steps

  • Record the state of the algorithm at each step or iteration

• Each stage of the algorithm is executed step by step.

• Inputs, outputs, variables and processes can be checked for the correct value when the stage is completed

Trace table walkthrough

• Below is a flowchart to determine the highest number of ten user-entered numbers

• The algorithm prompts the user to enter the first number which automatically becomes the highest number entered

• The user is then prompted to enter nine more numbers.

  • If a new number is higher than an older number then it is replaced

• Once all ten numbers are entered, the algorithm outputs which number was the highest

• Example test data to be used is: 4, 3, 7, 1, 8, 3, 6, 9, 12, 10