User`s guide

7. Select the "Image file ---> Diskette" option, follow prompts, and you should
end up with a good diskette. (If everything seemed to go well but the disk does
not work, try repeating the process using the other "Order" option.)
DSK2FILE and ASIMOV can, also, create disk image (.dsk or .po) files.
Similarly, using ADT to transfer a 5.25" disk automatically creates a .dsk disk
image on the PC. The source disk can be for a game, etc. so long as the diskette
is not copy protected.
Note: DOS 3.3 products which depend upon Volume numbering to identify diskettes
will normally not work in disk image form on an Apple II emulator because Volume
number information is embedded in non-data parts of a disk and is not included
in a standard .dsk disk image file.
NIB (.nib)
Some copy protected diskettes can be converted to another kind of disk
image called "NIB". Saltine's Super Transcopy (SST) incorporates bit copy
routines to attempt to produce a nibblized disk image of a 5.25" diskette.
On your Apple II, SST reads the disk bytes from half a disk and stores that
data on a whole normal disk. Then it does the same for the second half. These
two disks can be converted to .dsk disk images and moved to a PC or Mac. There,
the .dsk images are merged into a NIB image using SST running on an emulator.
If successful, you have a .nib file which can be used like a diskette on
popular Apple II emulators. (For one or two older emulators, .nib files are the
only useable images.)
The standard length of a .nib file is 232,960 bytes-- much larger than a
DSK. However, since .nib files include sector address header and other non-data
'embedded' diskette information, they can be used to image many protected disks.
Naturally, a .nib file preserves DOS 3.3 volume numbering. This allows
programs which use volume numbers to identify their disks to run on emulators.
Many disks with no copy protection are in .nib form instead of .dsk because the
game, etc. which uses the disks needs to check volume numbering.
2MG (.2mg; sometimes .2img)
Today, more and more IIgs software is being converted to 2MG disk image
format used on XGS and other IIgs emulators. These are .dsk or .nib images with
a prefix (usually 64 bytes) which includes information about size, format,
sector ordering, volume number, locked/unlocked, etc..
2MG files may also have a Comment and/or extra file information added
following the disk image data. The format can accommodate disk images ranging
from 5.25" diskette up through hard disk. For 2MG format details, see
http://apple2.org.za/gswv/a2zine/Docs/DiskImage_2MG_Info.txt .
The usual length of an 800k .2MG image (with no Comment or extra data) is
819,264 bytes*.