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hippietrail
hippietrail
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I'm interested in working with the most common Apple II disk image file format, .dsk.

(I only programmed these machines briefly in Basic around 1979-81 and have not been in the emulator scene, so I'm pretty ignorant of much technical stuff.)

So .dsk files are raw dumps of disk contents with no headers to describe them. But they come in two flavours, one for DOS and one for ProDOS, the two common disk operating systems on the 8-bit Apple II.

.do is the unambiguous file extension for DOS format, in which the image file is a raw dump of the physical 256-byte disk sectors in order.

.po is the unambiguous file extension for ProDOS format, in which the image file is a raw dump of the logical 512-byte disk blocks in order.

I haven't yet learned much about DOS or ProDOS or how either structures the disk. I don't even know if they have partially compatible structures, such as whether they put the directory in the same place in the same format.

So I'd like to know if there is a technique for examining the bytes of a .dsk image to know whether I should proceed to process it as a DOS .do or as a ProDOS .po.

I'm interested in working with the most common Apple II disk image file format, .dsk.

(I only programmed these machines briefly in Basic around 1979-81 and have not been in the emulator scene, so I'm pretty ignorant of much technical stuff.)

So .dsk files are raw dumps of disk contents with no headers to describe them. But they come in two flavours, one for DOS and one for ProDOS, the two common disk operating systems on the 8-bit Apple II.

.do is the unambiguous file extension for DOS format, in which the image file is a raw dump of the disk sectors in order.

.po is the unambiguous file extension for ProDOS format, in which the image file is a raw dump of the disk blocks in order.

I haven't yet learned much about DOS or ProDOS or how either structures the disk. I don't even know if they have partially compatible structures, such as whether they put the directory in the same place in the same format.

So I'd like to know if there is a technique for examining the bytes of a .dsk image to know whether I should proceed to process it as a DOS .do or as a ProDOS .po.

I'm interested in working with the most common Apple II disk image file format, .dsk.

(I only programmed these machines briefly in Basic around 1979-81 and have not been in the emulator scene, so I'm pretty ignorant of much technical stuff.)

So .dsk files are raw dumps of disk contents with no headers to describe them. But they come in two flavours, one for DOS and one for ProDOS, the two common disk operating systems on the 8-bit Apple II.

.do is the unambiguous file extension for DOS format, in which the image file is a raw dump of the physical 256-byte disk sectors in order.

.po is the unambiguous file extension for ProDOS format, in which the image file is a raw dump of the logical 512-byte disk blocks in order.

So I'd like to know if there is a technique for examining the bytes of a .dsk image to know whether I should proceed to process it as a DOS .do or as a ProDOS .po.

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hippietrail
hippietrail
  • 7.9k
  • 2
  • 23
  • 72

How can I programmatically determine whether an Apple II .dsk disk image is a DOS .do image or a ProDOS .po image?

I'm interested in working with the most common Apple II disk image file format, .dsk.

(I only programmed these machines briefly in Basic around 1979-81 and have not been in the emulator scene, so I'm pretty ignorant of much technical stuff.)

So .dsk files are raw dumps of disk contents with no headers to describe them. But they come in two flavours, one for DOS and one for ProDOS, the two common disk operating systems on the 8-bit Apple II.

.do is the unambiguous file extension for DOS format, in which the image file is a raw dump of the disk sectors in order.

.po is the unambiguous file extension for ProDOS format, in which the image file is a raw dump of the disk blocks in order.

I haven't yet learned much about DOS or ProDOS or how either structures the disk. I don't even know if they have partially compatible structures, such as whether they put the directory in the same place in the same format.

So I'd like to know if there is a technique for examining the bytes of a .dsk image to know whether I should proceed to process it as a DOS .do or as a ProDOS .po.