<Ok, so on my distribution disk if I boot it up it comes up as RT-11 V20B S <but if I boot DXMNTFB.SYS it comes up RT-11 V20B FB. What's the difference <Floating point? Not floating point. SJ is the single job monitor FB is the forground background monitor (spooling to printer is a good background task! Lator versions will have: BM batch monitor (for a batch based system) XM extended memory monitor Other possibilities are also possible via a build. Allison