Please refer to the documentation for any ambiguities.
Universal Disk Images (.2mg or .2img) consist of a 64-byte header followed by disk image data. An optional comment chunk and creator-specific chunk (in that order) may be present after the image data.
All values are stored in little endian format.
| Name | Offset | Size |
|---|---|---|
| magic_code | $00 | 4 bytes |
| creator_code | $04 | 4 bytes |
| header_length | $08 | 2 bytes |
| version | $0a | 2 bytes |
| format | $0c | 4 bytes |
| flags | $10 | 4 bytes |
| blocks | $14 | 4 bytes |
| data_offset | $18 | 4 bytes |
| data_length | $1c | 4 bytes |
| comment_offset | $20 | 4 bytes |
| comment_length | $24 | 4 bytes |
| creator_offset | $28 | 4 bytes |
| creator_length | $2c | 4 bytes |
| reserved | $30 | 16 bytes |
magic_code
This is the string '2IMG'.
creator_code
This is a four-character tag which identifies the file creator. Currently know values are:
| Application | Code |
|---|---|
| Bernie ][ the Rescue | B2TR |
| Catakig | CTKG |
| Sheppy's ImageMaker | ShIm |
| Sweet 16 | WOOF |
| ProFUSE | PRFS |
header_length
This is the length of the header. Although the documentation specifies 52 (which excludes reserved bytes), some files are known to use 64.
version
The version number of the image file. This should be 1.
image_format
The image data format. Valid values are:
| Format | Value |
|---|---|
| DOS 3.3 Order | 0 |
| ProDOS Order | 1 |
| Nibblized data | 2 |
flags
Bit flags pertaining to the disk image. Undefined bits should be set to 0.
| Bit | Description |
|---|---|
| 31 | If this bit is set, the disk is locked. |
| 8 | If this bit is set, bits 0--7 are valid. If this bit is not set, a volume number of 254 should be assumed |
| 0--7 | The DOS 3.3 volume number (0--254). Only valid if bit 8 is set |
blocks
The number of 512-byte blocks in the disk image. For Non-ProDOS Order disk images, this field should be 0.
data_offset
Offset to the first byte of the image data. The image data must come before the comment data and the creator data (if present).
data_length
Length of the image data in bytes. For ProDOS Order disk image, this should be blocks * 512.
comment_offset
Offset to the first byte of the comment data. May be 0 if there is no comment.
comment_length
Length of the comment data. May be 0 if there is no comment.
creator_offset
Offset to the first byte of the creator-specific data. May be 0 if there is no creator-specific data.
creator_length
Length of the creator-specific data. May be 0 if there is no creator-specific data.