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An ISO image is an archive file of an optical disc, a type of disk image composed of the data contents from every written sector on an optical disc, including the optical disc file system.〔 Definition: An ISO file, often called an ISO image, is in fact an "image" of an entire CD or DVD. The entire contents of a disc can be represented in a single ISO file.〕 ISO image files usually have a file extension of ''.iso''. The name ''ISO'' is taken from the ISO 9660 file system used with CD-ROM media, but what is known as an ISO image might also contain a UDF (ISO/IEC 13346) file system (commonly used by DVDs and Blu-ray Discs). ISO images can be created from optical discs by disk imaging software, or from a collection of files by optical disc authoring software, or from a different disk image file by means of conversion. Software distributed on bootable discs is often available for download in ISO image format. And like any other ISO image, it may be written to an optical disc such as CD or DVD. == Description == There is no standard definition for ISO image files. ISO disc images are uncompressed and do not use a particular container format; they are a sector-by-sector copy of the data on an optical disc, stored inside a binary file. ISO images are expected to contain the binary image of an optical media file system (usually ISO 9660 and its extensions or UDF), including the data in its files in binary format, copied exactly as they were stored on the disc. The data inside the ISO image will be structured according to the file system that was used on the optical disc from which it was created. ISO files store only the user data from each sector on an optical disc, ignoring the control headers and error correction data, and are therefore slightly smaller than a raw disc image of optical media. Since the size of the user data portion of a sector (logical sector) in data optical discs is 2,048 bytes, the size of an ISO image will be a multiple of 2,048. The ''.iso'' file extension is the one most commonly used for this type of disc images. The ''.img'' extension can also be found on some ISO image files, such as in some images from Microsoft DreamSpark; however, IMG files, which also use the ''.img'' extension, tend to have slightly different contents. The ''.udf'' file extension is sometimes used to indicate that the file system inside the ISO image is actually UDF and not ISO 9660. Any single-track CD-ROM, DVD or Blu-ray disc can be archived in ISO format as a true digital copy of the original. Unlike a physical optical disc, an image can be transferred over any data link or removable storage medium. An ISO image can be opened with almost every multi-format file archiver. Native support for handling ISO images varies from operating system to operating system. Hybrid disc formats include the ability to be read by different devices, operating systems, or hardware. In the past, one example of this use was for a disc that supported both Microsoft Windows and Macintosh installations from a single disk image (by containing several file systems). An ISO can be "mounted" with suitable driver software, i.e. treated by the operating system as if it were a physical optical disc. Most Unix-based operating systems, including GNU/Linux and Mac OS X, have built-in capability to mount an ISO. Windows 8 also has such capability. For other operating systems software drivers can be installed to achieve the same objective. Since there is no standard defining the ISO disc image file format, the term "ISO image" is sometimes used in a broader sense to refer to any disc image file of an optical disc, independent of the format it uses. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ISO image」の詳細全文を読む スポンサード リンク
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