I guess I'm not allowed a convenient memory lapse.DOS-11 predates RSX & Files-11. It has a MFD/UFD directory structure, vaguely echoing TOPS-10. I think that the 14-bye tape file header is most of the directory entry from the on-disk DOS-11 structure. This caused some grief on tape, as the ANSI standard (and some drives/drivers) require a minimum record length of 18 bytes; thus the directory entries on MM could be skipped as 'noise records'.
The DECtape file structure for DOS-11 is documented in http://bitsavers.trailing-edge.com/pdf/dec/pdp11/dos-batch/DOS_CourseHandouts.pdf, mostly in http://bitsavers.trailing-edge.com/pdf/dec/pdp11/dos-batch/DosBatchHandbook_v9_Apr74/02.pdf, with other random bits in the other chapters.
It's not the same as RSX or RT. Different design goals - and different engineering groups :-)
DOS was serially multi-user. So it had permissions, contiguous and linked files. RT single user; no permissions, contiguous only. RSX got Files-11 - the everything to everyone format - at the cost of ACPs, complexity and memory.
I think - but I'd have to dissect a tape - that KLDCP used the DOS file structure on -11 DECtape for simplicity, and the fact that there were interchange programs (flx,etc) that could read/write them on the other OSs. It was the least common denominator file structure.
Of course, DTAs were so slow and expensive that you wanted to run from disk instead, even when floppies replaced DECtape as the KL's front-end device.
In any case, the simh problem appears to be a low-level format emulation; my remarks on the file structure were only provided to assist in identifying the data.
This communication may not represent my employer's views, if any, on the matters discussed. On 28-Mar-13 15:19, Johnny Billquist wrote:
On 2013-03-28 19:23, Timothe Litt wrote:Good information, but this thread is about DECtape, not 9-Track magtapes...Right.The format looks about right for 9-track DOS-11 magtapes; I remember writing code to extract files from them on the -10. It's not right (or at least, not complete) for the block-addressable DECtapes.DECtapes (atleast on RSX) are Files-11 ODS-1 volumes, and not ANSI labelled tapes. They have nothing in common with each other, apart from both being tapes. The closest relative to a DECtape is a floppy.Also, the DOS-11 tape format is not the same as ANSI labelled tapes. They are not compatible.In RSX, ANSI labelled tapes are accessed through MTAACP, and the tapes are mounted as a known format. You then access them with the normal tools you'd use for any normal work in RSX. (Such as PIP.) DOS-11 tapes are instead mounted foreign, and you need FLX to read/write to them.JohnnyI don't think DOS-11 would have been documented in any of the references cited. There's now a SIMH repo on github; your utility could go into the tools section. This communication may not represent my employer's views, if any, on the matters discussed. On 28-Mar-13 14:09, Larry Baker wrote:On 28 Mar 2013, at 5:24 AM, <[email protected] <mailto:[email protected]>> <[email protected] <mailto:[email protected]>> wrote:Google 'AA-JS16A-TC' for some Files-11 format information; I'd have to think a bit on the DOS-11 format.RSX/VMS Files-11 tapes are ANSI labeled tapes. I know OpenVMS also used HDR3/4 labels for RMS information. There was a MOUNT option to suppress writing those labels. I wrote an RSX/VMS program that will scan an unknown tape and decode it for you. (If anyone wants it, let me know where I should upload it.) The DOS format decoder looks for a 14 byte (physical) record at the start of the file. It is decoded by the following code: C C... DEC DOS labels C Call R50ASC ( 6, buffer( 1), ascbuf( 1) ) Call R50ASC ( 3, buffer(13), ascbuf( 7) ) ascbuf(10) = '.' Call R50ASC ( 3, buffer( 5), ascbuf(11) ) ltemp(1) = buffer(7) ltemp(2) = 0 mem = itemp ltemp(1) = buffer(8) grp = itemp ltemp(1) = buffer(11) ltemp(2) = buffer(12) jday = MOD(itemp,1000) year = itemp/1000 + 70 Call JDCONV ( jday, mon, day, year ) ltemp(1) = buffer( 9) ltemp(2) = buffer(10) Write (STDOUT,619) ifile, grp, mem, ascbuf, day, month(mon), 1 year, itemp 619 Format (//' File ', I4, ':', T34, '"', '[', O3.3, ',', O3.3, ']', 1 13A1, 2X, I2, '-', A, '-', I2.2, ' <', O3.3, '>', '"') The DOS label contents are: Words 1-2 RAD50 characters 1-6 of the file name part (before the implied period) Word 3 RAD50 characters 1-3 of the file type (after the implied period) Word 4 Octal File owner's User Identification Code (group code in high-order byte, member code in low-order byte)Word 5 Binary File creation date ( 1000 * ( year - 1970 ) + Julian day )Word 6 Octal File protection (low-order to high-order RWED bits: read, write, extend, delete; grouped low-order to high-order for system, owner, group, world) Word 7 RAD50 characters 7-9 of the file name part (before the implied period) The references I used to write the program (back in the 1980's) are below. Which reference had the DOS label format I don't remember (if any of them did). 6 References [1] American National Standards Institute, 1978, Magnetic Tape Labels and File Structure for Information Interchange (ANSI X3.27-1978). [2] Digital Equipment Corp., 1985, RSX-11M/M-Plus MCR Operations Manual (Order no. AA-FD10A-TC). [3] Digital Equipment Corp., 1985, RSX-11M-Plus Command Language Manual (Order no. AA-FD04A-TC). [4] Digital Equipment Corp., 1985, RSX-11M/M-Plus and Micro/RSX I/O Operations Reference Manual (Order no. AA-FD14A-TC). [5] Digital Equipment Corp., 1985, RSX-11M/M-Plus I/O Drivers Reference Manual (Order no. AA-FD09A-TC). [6] Digital Equipment Corp., 1984, VAX/VMS Command Definition Utility Reference Manual (Order no. AA-Z408A-TE). [7] Digital Equipment Corp., 1986, VAX/VMS DCL Dictionary (Order no. AA-Z200C-TE). [8] Digital Equipment Corp., 1984, VAX/VMS Mount Utility Reference Manual (Order no. AA-Z424C-TE). [9] Digital Equipment Corp., 1986, Guide to VAX/VMS Disk and Magnetic Tape Operations (Order no. AI-Y506B-TE). [10] Digital Equipment Corp., 1986, VAX/VMS I/O User's Reference Manual: Part I (Order no. AA-Z600C-TE). [11] International Business Machines Corp., 1978, OS/VS Tape Labels (Order No. GC26-3795-1). Larry Baker US Geological Survey 650-329-5608 [email protected] <mailto:[email protected]> _______________________________________________ Simh mailing list [email protected] http://mailman.trailing-edge.com/mailman/listinfo/simh_______________________________________________ Simh mailing list [email protected] http://mailman.trailing-edge.com/mailman/listinfo/simh
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