The Amazon's Kindle e-book reader stores books as digital data; it handles a limited set of file types, which helps keep format compatibility problems under control. Amazon codes the e-books and periodicals you purchase into proprietary formats called AZW and KF8. In addition to these, the Kindle reads standard TXT files and PDFs. As of September 2012, it does not support the EPUB e-book standard format.
AZW and KF8
Amazon originally offered e-books in the AZW file type it developed especially for Kindle readers. AZW files contain a book's text and a flexible formatting system that allows readers to change the font size to suit their vision needs. With the introduction of the Kindle Fire in September 2011, Amazon added a new format, KF8, which incorporates HTML and CSS techniques developed for the Web. Both AZW and KF8 use digital rights management technology, which enforces copy protection and discourages unauthorized copying and sharing.
MOBI and PRC
AZW has its roots in an earlier e-book format called MOBI, from the French company, Mobipocket. The Kindle can open MOBI files, but only those not protected by Mobipocket's own version of DRM. PRC is an e-book format related to MOBI; Kindles can open these files also, as long as they do not contain DRM.
Adobe helped popularize its PDF file format by offering free versions of its Acrobat program. As a result, millions of documents, including e-books, business reports, loan application forms and technical specification sheets are widely available over the Web as PDFs. Though Amazon does not sell books in this format, it included a PDF reader in its Kindle devices as a convenience.
A plain text file is a simple list of characters with no formatting, fonts or graphics; it is the most basic type of document file possible. Virtually every kind of computer and operating system recognizes the TXT file type. Software developers frequently place important information in TXT files because you don't need a special proprietary program to read them. Because many important legacy documents are plain text files, the Kindle supports this file type.
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