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Next: Series Minimum and Maximum
Up: Verifying the correctness of
Previous: Verifying the correctness of
Another way of testing the logic of programs is to carry out a desk-check, that is execute the statements of the algorithm yourself on a sample data set. This method of course is not foolproof, you would have to be sure that you traversed all possible paths through your algorithm, this might require you to use many data sets. It is useful to use a tabular layout for this. For example say the initial data file was
2 6 eofthen a tabular layout as follows could be used:
file number count total average
2 6 eof before initialisation
*
2 6 eof 0 0 after initialisation
*
2 6 eof 2 1 2 after first loop execution
*
2 6 eof 6 2 8 after second loop execution
*
2 6 eof 6 2 8 4 exit loop, evaluate average
The * indicates the file element which is available for reading
on the next input statement. Obviously this gives the correct result
for this file. This simple file is adequate to check the general case
here because there are only two paths through this algorithm. The
other path is the case where the file is empty. This could be checked
in the same way.