2006-07-08 15:41:03 +00:00
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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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 contained 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 143,488 or 143,616 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 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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2012-08-12 10:04:44 +00:00
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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;">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 harddisk 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</li>
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<li>.zip, .dsk.zip, .nib.zip, .2mg.zip</li>
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</ul>
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</p>
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2006-07-08 15:41:03 +00:00
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</body>
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</html>
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