ISO Image is uncompressed – sector by sector copy

ISO image – Wikipedia, the free encyclopedia

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.

(Extracted from https://en.m.wikipedia.org/wiki/ISO_image on March 9th, 2016 at 03:30 AM)