# Disk Images Help

Disk images are files on your computer that were converted from the floppy disks that you originally used with the Apple //e. The Apple //e computer usually came with 2 disk drives (A & B) that were connected in slot 6 on the motherboard.

Apple2Mac can read and write disk images in DOS-order (file extensions of .dsk and .do) or disk images that are raw nibble-encoded (file extension .nib). In the disk selection window you can specify whether they are inserted read-only or read+write in either disk drive A or drive B.

NOTE: ProDOS-order and other image formats are planned for future releases of the emulator.

## Procuring Disk Images

Disk images can be procured from various online sources. In particular, you can use anonymous FTP to the Apple2 archive at ftp.apple.asimov.net.

## Troubleshooting Disk Images

If you have a disk image that appears problematic, (won't boot or errors out), it may be one of several things:

- You have "inserted" the disk in a read-only mode, and you are attempting to write information to that disk. Usually the game or app will complain if it needs write access, but not always. Open the disks dialog and select read/write status for that disk image file.
- The disk image itself is corrupted. If you suspect Apple2Mac is reponsible, please file an issue report on Github.
- There is a bug in the emulator. Check the Github issues page to see the status of known issues.

Some games make use of both disk drives, but only if a disk image was loaded into the second disk drive. For example you might load the "boot" disk in drive A, and the "player" disk in drive B before booting the emulator.

## More Disk Image Info

Disk images are binary files that actually are raw dumps of the original 5.25" disk. A disk image will contain all tracks from 0 to 34. For the standard 143360 byte .dsk format each track is partitioned into sectors numbered from 0 to 15. Each sector is 256 bytes.

Emulated diskettes MUST have the .dsk or .nib extension (143360 bytes or 232960 bytes respectively), otherwise the emulator will not recognize the file as a valid diskette. However, it is valid to compress them by using gzip (then the extension becomes .dsk.gz or .nib.gz). The emulator will automatically decompress/compress them whenever required.