Amiga Disk File
Encyclopedia
Amiga Disk File aka ADF is a file format used by Amiga
computers and emulator
s to store images of disks
. It has been around almost as long as the Amiga itself, although it was not initially called by any particular name. Before it was known as ADF, it was used in commercial game production, backup and disk virtualization. Technically speaking, ADF is not really a file format
but actually a track-by-track dump of the disk data as read by the Amiga operating system, and so the "format" is really fixed-width AmigaDOS
data tracks appended one after another and held in a file.
0 to 79 of a standard 3.5" double density floppy disk, also called an 880 KB
disk in Amiga terms. The size of an ADF will vary depending on how many tracks have been imaged, but in practice it is unusual to find ADF files that are not 901120 bytes in size (80 cylinders × 2 heads
× 11 sectors
× 512 bytes/sector).
Most Amiga programs were distributed on double density floppy disks. There are also 3.5" high density floppy disks, which hold up to 1.76 MB
of data, but these are uncommon. The Amiga also had 5.25" double density disks. The WinUAE Amiga emulator supports all three disk formats, but 3.5" double density is the most common.
ADF files can be downloaded and copied to Amiga disks with the EasyADF application and various applications freely available on the Internet.
There is a program called ADF Opus, which is a Microsoft Windows
–based program that allows people to create their own ADF files. This program supports creating double density (880 KB ADF files, the most common) and high density (1.76 MB) ADF files. ADF Opus also allows people to convert ADF files into ADZ files.
There is also a GPL command line program called unADF, which allows you to extract files from a ADF file.
with gzip
. The typical file extension is ".adz", derived from ".adf.gz".
format tracks. Disks with non-standard tracks may be available in ADF format, albeit cracked
in order to create a regular AmigaDOS volume. However, the Amiga itself was not limited to storing data in these standard tracks. The Amiga's floppy disk controller
was very basic but transparent, and for that reason very flexible allowing disks of other and custom formats to be read and written as well. Disk handling is not locked down like the one in a modern PC
, and so most of the work to read and write disks is done by the operating system itself . However, because programmers did not have to use the operating system routines, it was quite normal for games developers to create their own disk formats and also apply many different sorts of copy protection
. As it was, most full-price commercial Amiga games had some form of custom disk format and/or copy protection on them. For this reason, most commercial Amiga games cannot be stored in ADF files unaltered, but there is an alternative called Interchangeable Preservation Format (IPF) which was specifically designed for this purpose.
The Software Preservation Society
Interchangeable Preservation Format (.IPF) is an open format for which the source code of the official library is available.
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
computers and emulator
Emulator
In computing, an emulator is hardware or software or both that duplicates the functions of a first computer system in a different second computer system, so that the behavior of the second system closely resembles the behavior of the first system...
s to store images of disks
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
. It has been around almost as long as the Amiga itself, although it was not initially called by any particular name. Before it was known as ADF, it was used in commercial game production, backup and disk virtualization. Technically speaking, ADF is not really a file format
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...
but actually a track-by-track dump of the disk data as read by the Amiga operating system, and so the "format" is really fixed-width AmigaDOS
AmigaDOS
AmigaDOS is the disk operating system of the AmigaOS, which includes file systems, file and directory manipulation, the command-line interface, and file redirection....
data tracks appended one after another and held in a file.
ADF
Most ADF files are images of the Amiga-formatted tracks held on cylinderCylinder (disk drive)
A disk drive cylinder is a division of data in a disk drive, as used in the CHS addressing mode of a Fixed Block Architecture disk or the cylinder–head–record addressing mode of a CKD disk. The concept is concentric, hollow, cylindrical slices through the physical disks , collecting the respective...
0 to 79 of a standard 3.5" double density floppy disk, also called an 880 KB
Kibibyte
The kibibyte is a multiple of the unit byte for quantities of digital information. The binary prefix kibi means 1024; therefore, 1 kibibyte is . The unit symbol for the kibibyte is KiB. The unit was established by the International Electrotechnical Commission in 1999 and has been accepted for use...
disk in Amiga terms. The size of an ADF will vary depending on how many tracks have been imaged, but in practice it is unusual to find ADF files that are not 901120 bytes in size (80 cylinders × 2 heads
Disk read-and-write head
Disk read/write heads are the small parts of a disk drive, that move above the disk platter and transform platter's magnetic field into electrical current or vice versa – transform electrical current into magnetic field...
× 11 sectors
Disk sector
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. Each sector stores a fixed amount of user data. Traditional formatting of these storage media provides space for 512 bytes or 2048 bytes of user-accessible data per sector...
× 512 bytes/sector).
Most Amiga programs were distributed on double density floppy disks. There are also 3.5" high density floppy disks, which hold up to 1.76 MB
Mebibyte
The mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220, therefore 1 mebibyte is . The unit symbol for the mebibyte is MiB. The unit was established by the International Electrotechnical Commission in 2000 and has been accepted for use by all major...
of data, but these are uncommon. The Amiga also had 5.25" double density disks. The WinUAE Amiga emulator supports all three disk formats, but 3.5" double density is the most common.
ADF files can be downloaded and copied to Amiga disks with the EasyADF application and various applications freely available on the Internet.
There is a program called ADF Opus, which is a Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
–based program that allows people to create their own ADF files. This program supports creating double density (880 KB ADF files, the most common) and high density (1.76 MB) ADF files. ADF Opus also allows people to convert ADF files into ADZ files.
There is also a GPL command line program called unADF, which allows you to extract files from a ADF file.
ADZ
An ADZ file is an ADF file that has been compressedData compression
In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....
with gzip
Gzip
Gzip is any of several software applications used for file compression and decompression. The term usually refers to the GNU Project's implementation, "gzip" standing for GNU zip. It is based on the DEFLATE algorithm, which is a combination of Lempel-Ziv and Huffman coding...
. The typical file extension is ".adz", derived from ".adf.gz".
IPF
The ADF file format can only store disks that have legal AmigaDOSAmigaDOS
AmigaDOS is the disk operating system of the AmigaOS, which includes file systems, file and directory manipulation, the command-line interface, and file redirection....
format tracks. Disks with non-standard tracks may be available in ADF format, albeit cracked
Software cracking
Software cracking is the modification of software to remove or disable features which are considered undesirable by the person cracking the software, usually related to protection methods: copy protection, trial/demo version, serial number, hardware key, date checks, CD check or software annoyances...
in order to create a regular AmigaDOS volume. However, the Amiga itself was not limited to storing data in these standard tracks. The Amiga's floppy disk controller
Floppy disk controller
A floppy disk controller is a special-purpose chip and associated disk controller circuitry that directs and controls reading from and writing to a computer's floppy disk drive . This article contains concepts common to FDCs based on the NEC µPD765 and Intel 8072A or 82072A and their descendants,...
was very basic but transparent, and for that reason very flexible allowing disks of other and custom formats to be read and written as well. Disk handling is not locked down like the one in a modern PC
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...
, and so most of the work to read and write disks is done by the operating system itself . However, because programmers did not have to use the operating system routines, it was quite normal for games developers to create their own disk formats and also apply many different sorts of copy protection
Copy protection
Copy protection, also known as content protection, copy obstruction, copy prevention and copy restriction, refer to techniques used for preventing the reproduction of software, films, music, and other media, usually for copyright reasons.- Terminology :Media corporations have always used the term...
. As it was, most full-price commercial Amiga games had some form of custom disk format and/or copy protection on them. For this reason, most commercial Amiga games cannot be stored in ADF files unaltered, but there is an alternative called Interchangeable Preservation Format (IPF) which was specifically designed for this purpose.
The Software Preservation Society
Software Preservation Society
The Software Preservation Society , formerly known as the Classic Amiga Preservation Society , is a group of computer enthusiasts that is concentrating on finding old software disks and taking a snapshot of the disks in a format that can be preserved for the future...
Interchangeable Preservation Format (.IPF) is an open format for which the source code of the official library is available.