"Julian Wolfe" <fireflyst at earthlink.net> wrote: As others have said, CIS stands for Commercial Instruction Set. It's an add-on to the PDP-11 for string manipulation. It's entirely described in a number of versions of the PDP-11 processor handbook. Probably any version dealing with the 11/44, 11/23 or 11/24, since those were the only CPUs to have CIS (if we ignore the 11/74). Further comments on this thread: An 11/44 cannot have FIS. (Jeez, don't you know anything? :-) ) The FIS was an early floating point implementation which only exists for the 11/35, 11/40 and 11/03. All others use some variant of the FPP-11. Different opcodes, different data formats, different just about everything. RSTS/E in late versions use MOVC if it exists, to move data around in the kernel. RSX never use CIS in the kernel. Neither FORTRAN IV, FORTRAN 77, PDP-11, nor BASIC+2 uses CIS. They will all use FPP however, if it exists. FORTRAN IV can also use FIS, if I remember right. I don't think DIBOL uses CIS, but I'm not entirely sure. COBOL uses CIS if it exists, however. Of course an assembler programmer can use CIS if he wants to. :-) EAE is another beast, and one which any Unibus cpu probably can use, since it's not really an addition to the CPU, but actually a peripherial. Not much point in it, however, atleast not if you have EIS. Since that does more, better and faster than EAE. It was mostly something used in the 11/20 and 11/15. And e11 V5 actually have the 11/74 implemented, along with the other stuff needed for multiprocessor PDP-11s. And it works, even if it is a bit tricky to set up, and not really documented any good. Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at update.uu.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol