Adobe Digital Editions uses .epub format for its e-books, with digital rights management (DRM) protection provided through their proprietary ADEPT mechanism. The ADEPT framework and scripts have been reverse-engineered to circumvent this DRM system.
The Amazon Kindle can read unprotected .mobi files, as can Amazon's Kindle application for Windows and MacOS. Amazon has also developed an .epub to .mobi converter called KindleGen, and it supports IDPF 1.0 and IDPF 2.0 EPUB format.
The first e-books in history were in plain text (.txt) format, supplied for free by the Project Gutenberg community, but the format itself existed before the e-book era. The plain text format doesn't support digital rights management (DRM) or formatting options (such as different fonts, graphics or colors), but it has excellent portability as it is the simplest e-book encoding possible as a plain text file contains only ASCII or Unicode text (text files with UTF-8 or UTF-16 encoding are also popular for languages other than English). Almost all operating systems can read ASCII text files (e.g. Unix, Macintosh, Microsoft Windows, DOS and other systems) and newer operating systems support Unicode text files as well. The only potential for portability problems of ASCII text files is that operating systems differ in their preferred line ending convention and their interpretation of values outside the ASCII range (their character encoding). Conversion of files from one to another line-ending convention is easy with free software. DOS and Windows uses CRLF, Unix and Apple's OS X use LF, Mac OS up to and including OS 9 uses CR. By convention, lines are often broken to fit into 80 characters, a legacy of older terminals and consoles. Alternately, each paragraph may be a single line. 1e1e36bf2d