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ebook Formats

The ebook community has many options when it comes to choosing a format for production. While the average end user might arguably simply want to read books, every format has its exponents and champions, and debates over "which format is best" can become intense. For the average end user to read a book, every format has its advantages and disadvantages. Formats available include, but are by no means limited to:

Plain text
Published as an ASCII text (or .txt), an e-text in the proper (strict) sense.

Computer-encoded text that consists only of human-readable characters from a given standard, with no other formatting or structural information. Plain text interchange is commonly used between computer systems that do not share higher-level protocols. ISO 8859 is a group of related ISO standards for 8-bit character encodings for use by computers. These standards are based on ASCII, the most widely used 7-bit character encoding.

Image files
An ebook can be distributed as a sequence of images, one for each page. In this way, any image format can be used as an ebook format. This method of distribution produces files very much larger than all others, and also has the disadvantage that the user cannot select text, nor can the ebook be read by a screen reader. Distribution as images is most suitable for comic books, books about art, or other very visual works.

Rich Text Format
Published as an .rtf

A standard formalized by Microsoft Corporation for specifying formatting of documents. RTF files are actually ASCII files with special commands to indicate formatting information, such as fonts and margins.

Standard Generalized Markup Language
Commonly known as SGML

Standardized metalanguage for the description of markup languages; a set of rules for using whatever markup vocabulary is adopted. This includes the TEI standard.

eXtensible Markup Language
Published as an .xml

A subset of SGML constituting a particular text markup metalanguage for defining markup languages for the interchange of structured data. The Unicode Standard is the reference character set for XML content. XML is a trademark of the World Wide Web Consortium.

TeX
The TeX format is a popular academic format. TeX is a typesetting system written by Donald Knuth, especially for technical writing applications in the communities of mathematics, science, and computer science. TeX can typeset complex mathematical formulas, but is now also being used for many other typesetting tasks especially in template packages. LaTeX is a TeX document preparation system. LaTeX offers programmable features and facilities for automating aspects of typesetting and desktop publishing, especially numbering and cross-referencing, tables and figures, page layout, bibliographies. LaTeX was originally written in 1984 by Leslie Lamport and has become a leading method for using TeX; few people write in plain TeX any more. (current version: 2e)

PostScript
Published as an .ps

PostScript is a page description language used primarily in the electronic and desktop publishing areas for describing the contents of a printed page in a higher level than the actual output bitmap.

Portable Document Format
Published as an .pdf

A file format created by Adobe Systems, initially to provide a standard form for storing and editing printed publishable documents. Because documents in .pdf format can easily be seen and printed by users on a variety of computer and platform types, they are very common on the World Wide Web.

PDF files are created mainly using Adobe Acrobat, but Acrobat Capture and other Adobe products also support their creation, as do third-party products such as PDFCreator and OpenOffice.org. Acrobat Reader (now simply called Adobe Reader) is used to view PDF files. PDF files typically contain product manuals, brochures, magazine articles, or flyers as they can embed fonts, images, and other documents. A PDF file contains one or more page images, each of which you can zoom in on or out from. Acrobat PDF include interactive elements such as buttons for forms entry and for triggering sound and Quicktime or AVI movies. Acrobat PDF files are optimized for the Web by rendering text before graphic images and hypertext links. Adobe's PDF-like eBook format is incorporated into their reader.

DjVu
Published as .djvu

DjVu is a file format that has been long in obscurity (in other words, since 1996), but that is starting to surface now that free tools to manipulate the files are available.

DjVu is a format that particularly excels in storing scanned images. There are even advanced compressors especially specializing in low-color images, such as text documents. Individual files may contain single pages, or they can be collections of multiple pages.

The images are divided in separate layers (such as multi-color, low-resolution, lossily-compressed background layer, and few-colors, high-resolution, tightly-compressed foreground layer), each compressed in best applicable method. The files are also designed to decompress very fast, even faster than vector-based formats.

The advantage of DjVu is that it is possible to take a high-resolution scan (300-400 DPI), good enough for both on-screen and printing, and store it very efficiently. Several dozens of 300 DPI black-and-white scans can be stored in less than a megabyte.

Microsoft
Published as an .lit

The MS reader uses patented ClearType® display technology. Navigation works with a keyboard, mouse, stylus, or through electronic bookmarks. The Catalogue Library records reader books in a personalized "home page". A user can add annotations and notes to any page, create large-print eBooks with a single command, or create free-form drawings in the reader pages. A built-in dictionary allows the user to look up words.

eReader (formerly Palm Digital Media)
Published as a .pdb

eReader is a program for viewing Palm Digital Media electronic books. Versions are available for PalmOS, PocketPC, Symbian OS, Windows, and Macintosh. The reader shows text one page at a time as paper books do. eReader supports embedded hyperlinks and images. Most eReader formatted books are encrypted, with the key being the purchaser's full name and credit card number.

Mobipocket
Published as an .prc

The Mobipocket Reader has a home page library. Readers can add blank pages in any part of a book and add free-hand drawings. Annotations — highlights, bookmarks, notes, and drawings — can be applied, organized, and recalled from a single location. Mobipocket Reader has electronic bookmarks, appearing in the page margins. Dictionaries allow users to look up definitions through a built-in Lookup function.

The reader has a full screen mode for the reading experience and has Microsoft ClearType® support. On Palm OS, readers can use sub-pixel rendering with the MobiType® font. Mobipocket Reader is the only eBook Reader running on nearly all PDA types (Palm OS, Pocket PC and Windows CE, Tablet PC, Casio BE-300, Psion, Symbian OS Smartphones, Franklin eBookMan) and PCs.

The Mobipocket eBook format based on the Open eBook standard using XHTML can include JavaScript and frames for a dynamic display, which makes Mobipocket the best solution for professional content such as medical reference eBooks and dictionaries. It also supports native SQL queries to be used with embedded databases.

The Mobipocket encryption system is not a password based system. Its DRM relies on the PDA hardware serial number.

Mobipocket also provides a free eNews service. A reader can subscribe to notable periodicals, or create custom channels. Software on the PC updates the subscriptions and sends them automatically to the PDA.

ExeBook
Published as an .exe

ExeBook is a compiler that produces an ebook file that, when executed, produces a simulated book onscreen, complete with page texture. The etext is encrypted as graphic images so that automatic text copying is very difficult. The fear of exe files picking up viruses, however, is hampering its acceptance.

DesktopAuthor
Published as an .exe and .dnl

DesktopAuthor is an electronic publishing suite that allows creation of digital web books with virtual turning pages. Digital web books of any epublication type can be written in this format, including ebrochures, ebooks, digital photo albums, ecards, digital diaries, online resumes, quizzes, exams, tests, forms and surveys. DesktopAuthor packages the ebook into a ".dnl" or ".exe" book. Each can be a single, plain stand-alone executable file which does not require any other programs to view it. DNL files can be viewed inside a web browser or stand-alone via the DNL Reader.