What functions does project management software provide that you can not use other tools?

Software normally speeds up a process that humans could perform and PM software is no different. As a matter of fact, advanced project management training teaches formulas to manually calculate financial ratiOS for earned value and methods to calculate the critical path of a schedule - both good examples of PM software functions. However, where it could take a day to manually calculate a complicated critical path, the software does it in seconds.

Keep in mind, though: Knowledge about underlying functions is still important, even if the software does the number-crunching. It's like a calculator: it adds, subtracts, divides or multiples, but it does not substitute a person's decision which to use.