You are trying to compare apples to oranges. Melanies code (or anybodys code) will only be able to get you to half step mode. That's the digital limit. Anybody who talks about microstepping is in reality using a stepper motor as a magnetic voice coil between steps. By varying the amount of current to one energized coil vs the other energized coil you can get the N-S poles of the rotor to line up anywhere between the two energized poles of the stator. This is analog circuitry which is often programmed using an 8-bit DAC and thats where the 256 number fits into the equation as a step size.