Trace Tables

Trace tables are used to follow algorithms and make sure they perform the required task correctly. Test data is usually used in conjunction with a trace table to ensure the correctness of the algorithm. Manually tracing an algorithm with test data in this way is known as a dry run
Trace tables can be used with flowcharts or pseudocode or even real code if necessary
Trace tables can also be used to discover the purpose of an algorithm by showing output data and intermediary steps
Trace tables record the state of the algorithm at each step or iteration. The state includes all variables that impact the algorithms output as well as the output itself
A trace table is composed of columns where each variable and the output is a column
Whenever a value changes or an output is produced the relevant column and row is updated to reflect the change

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

Figure 1: A flowchart to determine the highest of ten user entered numbers

Trace table for Figure 1: Highest number
Count	Highest	Number	Output
1			Enter ten numbers
	4		Enter your first number
2		3	Enter your next number
3	7	7
4		1
5	8	8
6		3
7		6
8	9	9
9	12	12
10		10	12 is your highest number