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67896db65e
* Document the disk image size magic numbers (in source & help doc). * Mention 40+ tracks after oddball disk sizes. * Debugger 2.9.2.2: Fixed: DB HGR = 2000:3FFF was displaying help instead of being parsed. * Debugger 2.9.2.3: Fixed: DB HGR = 2000:3FFF and DB FOO = 300 wasn't parsing correctly from 2.9.1.3. Fix for commit 48e0fe3a. * Debugger: 2.9.2.4 Fixed: DA RESET = 3F2 was displaying help instead of being parsed. * Debugger: 2.9.2.5 Added: Symbol table for DOS 3.3 using file A2_DOS33.SYM2 * Debugger: 2.9.2.6 Added: QoL: Turning a symbol table on/off now shows the current status.
103 lines
4.4 KiB
HTML
103 lines
4.4 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
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<title>Disk Image Formats</title>
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</head>
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<body style="background-color: rgb(255, 255, 255); font-family: verdana;" alink="#008000" link="#008000" vlink="#008000">
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<h2><font color="#008000" face="Arial">Disk
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Image Formats</font></h2>
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<hr size="4">
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<p>Disk images can be in a number
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of different
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formats, depending on how they were created.</p>
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<p style="font-weight: bold;">DOS Order Images:</p>
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<p>DOS order disk images contain the data from
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each sector, stored in the same order that DOS 3.3 numbers
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sectors. If you run a DOS program on the Apple which reads in
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sectors one by one and then transfers them over a serial line to
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the PC, you will get a DOS order disk image. </p>
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<p>Apple floppy disks (normally) contain 35 tracks with
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16 sectors per track, for a total of 560 sectors. Each of these
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sectors contained 256 bytes of information, for a total of
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143,360 bytes per disk. Therefore, DOS order disk images are
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always at least 143,360 bytes long. Sometimes on the Internet you
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will see a disk image that is not 143,360 bytes long; this
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is probably a DOS order image with extra header information
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before or after the image. In most cases, AppleWin can
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automatically detect this and handle it. </p>
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<p>Due to some games being incorrectly converted to a disk image AppleWin also accepts disk images of sizes:
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<ul>
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<li>143,403 bytes (<i>Castle Wolfenstein</i>)</li>
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<li>143,488 bytes (<i>Rescue Raiders</i>)</li>
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</ul>
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<p>Some disk drives were able to handle 40+ tracks. AppleWin accept disk images up to 40 tracks -- 163,840 bytes -- as long as the disk image is a multiple of 4,096 bytes / track.</p>
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<p style="font-weight: bold;">ProDOS Order
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Images: </p>
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<p>ProDOS order disk images are very similar
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to DOS order images, except that they contain the sectors in the
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order that ProDOS numbers them. If you compress a disk with
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Shrinkit on an Apple, then transfer it over a modem and
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uncompress it on the PC, you will get a ProDOS order disk image. </p>
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<p>Since ProDOS order disk images contain the
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same information as DOS order disk images, simply in a different
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order, they are also about 143,360 bytes long. When you use a
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disk image of this size, AppleWin attempts to automatically
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detect whether it is in DOS order or ProDOS order by examining
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the contents of the disk. If the disk was formatted with a
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standard operating system such as DOS or ProDOS, AppleWin will
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successfully detect the format. Otherwise, it will revert to DOS
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order, which is by far the most common format. To force ProDOS
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order, give the file an extension of ".PO". </p>
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<p style="font-weight: bold;">Nibble Images:</p>
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<p>Nibble images contain all of the data on a
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disk; not just the data in sectors but also the sector headers
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and synchronization areas, all stored in the same encoded format
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that would be recorded on a real disk's surface. At 232,960
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bytes, nibble images are bigger than other images, but they can
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be useful for making images of copy protected software. </p>
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<p style="font-weight: bold;">2mg Images:</p>
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<p>2mg (or 2img) images are a wrapper around DOS, ProDOS or Nibble images.
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They contain extra meta-data describing for example, DOS volume number and
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write-protection.
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</p>
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<p style="font-weight: bold;">WOZ Images:</p>
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<p>The WOZ Disk Image format is an offshoot of the <A href="https://applesaucefdc.com/woz">Applesauce project</A>. Capturing highly accurate bit data is of no use if you don't have a container to hold the data. The WOZ format was designed to be able to contain every possible Apple ][ disk structure and layout. It can be so accurate that even copy protected software can't tell that it isn't an original disk.
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</p>
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<p style="font-weight: bold;">Compressed Images :</p>
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<p>All of the above can optionally be either gzip'ed or zipped. If a zip archive
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contains multiple files, then AppleWin only supports using the first file. For best results
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with hard disk images, uncompress first, as writing back to the image requires a full
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image re-compression after every block write. Examples of typical extensions are:
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<ul>
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<li>.gz, .dsk.gz, .nib.gz, .2mg.gz, .woz.gz</li>
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<li>.zip, .dsk.zip, .nib.zip, .2mg.zip, .woz.zip</li>
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</ul>
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</p>
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</body>
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</html>
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