I think Gary Kildall was very much into the PDP-8 when teaching at the Naval Post Graduate School in the early 70's (doing the FORTRAN/8 compiler for instance). Can't find the link now, but I read somewhere that his work with the 8008 and 8080 was guided by the idea of having a PDP-8 like machine in his home office. For CP/M's command syntax RT11 probably did not come into it. I just had a quick glance through the CP/M 1.4 - 2.2 manuals, and I did not see slash options (or any other option character). Microsoft bought QDOS as a base for PC-DOS/MS-DOS. The QDOS system calls were done such that converting existing 8080 CP/M code with Intel's source level 8080-to-8086 asm converter would generate the correct code. The FAT file system was modeled after the one used by MS Disk BASIC for the 8086. Not sure where the QDOS command line came from, other than CP/M. MS did a lot of its early development on a PDP-10: perhaps that was an inspiration too. Sorry for getting off-Unix-topic...