Systems with functionally designed parts easier to modify because each part is doing just that for which it is intended. Since the support of the program is greater than 3/4 life successful system, this feature is a decisive advantage. This also makes the system easy to understand and document, which also simplifies training. The result is that the practical lifetime of more functional [login to view URL] advantage for the realization is that if the software module has a single purpose, it will be easier and thus - it is easier and less expensive to design and [login to view URL] software systems, the function module will be easier to reuse because it is less likely to cause side effects that show up in other parts of the system.