From: schmidtd@my-deja.com   
      
   On 2/20/23 1:52 AM, Jens Gaulke wrote:   
   > Hi there,   
   >   
   > I'm writing an Apple II Emulator.   
   > [...]   
   > Where I am stuck is: How do I get a "disk image" in my emulation? Which   
   format must it have? Woz? DSK? Up to know I know "that these formats exist".   
   How can I deal with these formats? What do I have to consider?   
      
   I would start with what your goals are and work backwards from that.   
   The Disk II is an analog device at is core, and has various layers of   
   hardware, firmware, and software to decode the analog signal into a   
   stream of bits.  You can insert  your emulation at any level along that   
   spectrum, depending on the fidelity you are interested in achieving -   
   which will dictate the ultimate capabilities of your disk emulation (and   
   by extension, your emulator).   
      
   At one extreme is the ".dsk" which is only the bytes that the operating   
   system would ever present to a user; the data within all tracks and   
   sectors.  A layer beneath that is the nibble stream, represented by the   
   decoded nibbles that are actually recorded on a disk; that affords you   
   access to all the in-band data and enveloping headers and trailers.  And   
   beneath that is a ".woz" representation that defines lots more   
   meta-information about the recorded signals and their environment which   
   are important for encapsulating and decoding the many copy protection   
   schemes that were devised using the Disk II.  That level of information   
   isn't available in any other encoding.   
      
   The place to start getting a complete understanding of the physical Disk   
   II ecosystem is Sather's seminal work, Understanding the Apple II (and   
   Apple IIe) - chapter 9, "The Disk Controller".  That's every detail at   
   the bottom layer.   
      
   Sather's books (and more) are available here:   
   https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Books/   
      
   The Woz specification is available here:   
   https://applesaucefdc.com/woz/reference2/   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)