We use Mach 3 by Newfangled Solution LLC as the control software on our CNC machine tools. The flexibility and customisability of this package combined with the fact that it runs on Windows (XP, Vista, 7 and 8) makes for a very good solution despite the limitations imposed by being tied to a PC.
As time has progressed, the parallel port originally used for the control of the cnc machines through Mach3, has just about faded away. Software and hardware limitations have crept up on it and although the golden standard for many, including the Linux community, it now is not as common as it once was.
The SmoothStepper in action on our KRV2000
Thankfully vendors of solutions to the issue have emerged to ensure we are still able to use our beloved machines with newer operating systems and hardware.