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In comp.sys.apple2 Bill Garber <[EMAIL PROTECTED]> wrote: > You all are making DSK too complicated. All they are is this. > Track 1, sector 1, byte 1 is byte 1 of the file, and so on each byte > from the disk is sequential in the file. Nothing more. Track 0, sector 0, byte 0 starts at byte 0 of the file. This is because, for all possible sector skews, sector 0 is always in the same place. Track 0, sector 1, byte 0 could be in one of three different places. That's the difference between .PO, .DO, and Copy ][+ .IMG. If there were a CP/M disk-image utility you'd have four possibilities. A DOS utility will read sector 0 through sector 15 and write them out in that order. A ProDOS utility will read block 0 through block 7 and write them out as 512-byte blocks. Unfortunately, block 0 is track 0 sector 0 combined with track 0 sector 2, *not* track 0 sector 1. This means that disk images created with DOS RWTS-based utilities are different from images created with ProDOS utilities like ShrinkIt. CiderPress looks for DOS, ProDOS, Pascal, CP/M, and RDOS filesystems in "DOS", "ProDOS", and "physical" sector ordering every time you open a disk image. If the file has a helpful extension (like ".do"), it knows to try that first. However, until it successfully identifies a filesystem, it can't know the sector ordering, which is why for disks with no recognizable filesystem (like games with custom loaders) it will ask you to choose one. Because sector 0 is always in the right place, finding a DOS 3.3 VTOC isn't sufficient... we know it's DOS 3.3, but we don't know what order the sectors are, so it's necessary to examine the rest of the catalog track. Which gets even more fun when you deal with 32-sector images on 800K disks. Some formats, such as 2MG, are kind enough to tell you the order. Others, like ShrinkIt, are always ProDOS-order. In general, though, you have to keep poking at it until something looks familiar. -- Send mail to [EMAIL PROTECTED] (Andy McFadden) - http://www.fadden.com/ CD-Recordable FAQ - http://www.cdrfaq.org/ CiderPress Apple II archive utility for Windows - http://www.faddensoft.com/ Fight Internet Spam - http://spam.abuse.net/spam/ & http://spamcop.net/ Steve Conrad 810 Main Henrietta, MO 64036 816-494-5692 http://sasha91.0pi.com www.fortunecity.com/rivendell/stonekeep/600 It is no secret (nor should it come as any surprise) that humankind's most noble impulses often surface during the most trying of times, that human spirit rises to the challenge when faced with adversity, that human strength is born from human failings...Is it any wonder, then, that the SDF-1 crew became a tighter family after the fortress had been exiled than it had before? From the log of Captain (later Admiral) Henry Gloval -- Apple2list is sponsored by <http://lowendmac.com/> and... / Buy books, CDs, videos, and more from Amazon.com \ / <http://www.amazon.com/exec/obidos/redirect-home/lowendmac> \ Support Low End Mac <http://lowendmac.com/lists/support.html> Apple2list info: <http://lowendmac.com/lists/apple2.html> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/apple2list%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
