The results shown in this chapter suggest that for non-header files written in C language, all the complexity metrics are highly correlated with lines of code, and therefore the more complex metrics provide no further information that could not be measured simply with lines of code.
However, these results must be accepted with some caution. Header files show poor correlation between cyclomatic complexity and the rest of metrics. We argue that this is because of the nature of this kind of file. In other words, header files do not contain implementations, only specifications. We are trying to measure the complexity of source code in terms of program comprehension. Programmers must of course read and comprehend header files, which means that header files can contribute to complexity to a certain extent. However, even though cyclomatic complexity is poorly correlated with lines of code in this case, that does not mean that it is a good complexity metric for header files. On the contrary, the poor correlation is due only to the lack of control structures in header files. These files do not contain loops, bifurcations, etc., so their cyclomatic complexity will always be minimal, regardless of their size.
For nonheader files, all the metrics show a high degree of correlation with lines of code. We accounted for the confounding effect of size, showing that the high correlation coefficients remain for different size ranges.
In our opinion, there is a clear ...