ISO image

ISO image (german ISO image) is the name given to a computer file that contains a memory dump of the contents of a CD or DVD, which is structured in the format ISO 9660.

The file system is copied unchanged in the generation of an ISO image, thereby remain permissions and other metadata intact.

The standard ISO 9660 defines a file system for CDs or DVDs.

Implementation options

The making of an identical image can be done in many different ways. Firstly, "On-the -fly " to another means of creating an ISO file.

"On-the -fly "

The generation of an ISO image "on- the-fly " by means of two drives - one read and one write -enabled enabled. The reading of the original from the reader and the writing in the burner occur synchronously (analogous to the procedure for old audio cassettes). The reader must be sufficiently powerful (at least twice as fast as the burner ). The disk must not be damaged so that the necessary for writing constant data stream is guaranteed.

In such a process results in a 1:1 ( almost) exactly the same CD or DVD. In the strict sense must therefore be restrictive " almost equal " spoken of, because as good as any burning process is flawed. It is also possible that on the source CD errors by single scratches or dust and the like exist. If the error number does not exceed a critical level, ranging from the existing between the pure payload space to write in it information to correct or recover the user data without error from this. The space is in addition to the classification also used in data blocks, to accommodate additional bits, which allow the reconstruction of erroneous data ( forward error correction ) or can at least detect whether an error has occurred ( checksum). How can and should be the resulting errors were " eliminated " at each subsequent read operation.

ISO file

The route via an ISO file has several advantages:

ISO images in practice

An example downloaded ISO image can be opened with tools like IsoBuster or 7 -Zip. Nearly every burning program can burn an ISO image onto a medium. Starting with Windows 7, a corresponding burning program for Windows is included (Windows burner for disk images ). It is important that you do not burn the ISO file as a file on a medium, otherwise you still need a program to open the file and the medium also is not bootable.

With a virtual drive or a " loop device ", it is possible to mount an ISO image (mounting / mount ): The contents are then available in the file system; the original or a copy of the volume are then no longer necessary, nor appropriate drive.

In commercial CD-ROMs/DVDs, such as computer games, the possibility of creating ISO images are often affected by copyright protection method. Check Some computer games, if a virtual disk is installed and can not in this case start.