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It has been suggested that this article be merged into IMA (file format). (Discuss) Proposed since June 2011.

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The IMG file format is one of the following files:

1. A CD or DVD image file, essentially equivalent to an ISO file. On such a file, simply changing the extension from IMG to ISO can make it usable as the latter by most programs.
2. An archive format used for creating a disk image of floppy disks and HDDs. This allows for digital storage, transmission, and replication of floppy disks and HDDs. Files created using this format typically use the ".IMG" file extension. Please, note that there are at least two different kind of archives with this extension.
3. A file in the Macintosh Disk Image format used by Aladdin Systems (now Allume Systems) ShrinkWrap and Apple Disk Copy for Mac OS although they share the same file extension.
4. The IMG file format, also known as GEM IMG, is an image file format used to store bitmap digital images on Graphical Environment Manager.
5. A graphics image format used in various ways by many different graphics software packages.

IMG Archive Format details

The IMG file extension is used by, at least, two different file formats:

• An IMG file may contain a raw dump of the content of a disk. This format is not compatible with the Disk Copy Fast and DiskDupe format but is supported by multiple software vendors and conventions. It contains the same data as the IMA file format. In this case the image typically begins with a FAT boot sector, where the first byte is normally hexadecimal EB (code for a 8bit short jump, offset in the 2nd byte) with third byte 90 (code for a NOP), or rarely EA (code for a 16bit jump, offset in 2nd and 3rd byte). The file size will always be a multiple of the sector size — generally 512 bytes, but other sizes such as 128 and 1024 existed. More precisely the file size corresponds to Cylinders×Heads×(Sectors per track) sectors, e.g., 1440KB=80×2×18×512 for 80 cylinders (tracks) and 2 heads (sides) with 18 sectors per track.

• An IMG file may have been created by some popular MS-DOS tools like HDCopy which did not store a raw dump of the original disk, but a proprietary (compressed) form of it. In this case the first three bytes (noted in hexadecimal) of the image will be FF 18 07, and the file size can be anything.

Support and development

The raw IMG file format is currently supported by GNU RaWrite & RaWrite2, and RawWrite for Windows. It is utilized by Qemu, VirtualBox and WinImage.

Nero Burning ROM prior to 6.0 supported reading IMG file for creating bootable CD, but since then calls them IMA.

Please note that some popular DOS-based programs like HDCopy create archives with the same IMG file extension, but the file format is different. Those programs use a proprietary (and compressed) file format which is not a raw dump of the disk, so is not directly usable by RaWrite, VirtualBox, etc. You have to use HDCopy to restore the disk image with proprietary file format, and then create a raw dump of that to be readable by VirtualBox, WinImage, etc. You can use ImDisk or Virtual Floppy Drive to emulate a floppy drive under Windows.

Use

IMG files are used for:

• Digital storage, transmission, and replication of floppy disks.
• Mounting virtual floppy disk volumes.

See also

• mtools

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