An e-text (from "electronic text"; sometimes written as etext) is, generally, any text-based information that is available in a digitally encoded human-readable format and read by electronic means, but more specifically it refers to files in the ASCII character encoding.
E-text has the broad meaning of something electronic that represents words, a binary (or digital) version of a published work of text. Indeed, there are ASCII textbooks available. These are now referred to as, and the term is often used synonymously, an e-book.
The term e-text is used for the more limited case of data in ASCII text format, while the more general e-book can be in a specialized (and, at times, proprietary) file format. An ebook is commonly bundled by a publisher for distribution (as an ebook, an ezine, or an internet newspaper), whereas e-text is distributed in ASCII (or plain text). Metadata relating to the text is sometimes included with e-text (though it appears more frequently with ebooks).
Typically, e-text have some control characters such as tabs, line feeds and carriage returns without any embedded information such as font information, hyperlinks, or inline images. E-text files are files with generally a one-to-one correspondence between the bytes and ordinary readable characters such as letters and digits. Sometimes e-text files contain more than ASCII characters if they are encoded by East-Asian encoding (such as Shift JIS or unicode). If the e-texts are written in unicode, a UTF standard (such as UTF-8) defines the encoding format. Although e-text files are generally human-readable, they can of course be used for data storage by computer programs. Note that a webpage with formatted text is not an e-text specifically, but the HTML source code is; whether a file is an e-text thus may depend on the level on which one is considering it.
Most programming languages require source files to be stored in etext, as do HTML and XML. These files can be opened, read, and edited with a text editor. An e-text file can have the MIME type "text/plain", often with suffixes indicating an encoding. Common encodings for e-text include Unicode UTF-8, Unicode UTF-16/UCS-2, ISO/IEC 8859 and ASCII. Transferring e-text files between Unix, Macintosh and Microsoft Windows or DOS computers can be problematic, as each platform uses different control characters.
The added functionality (such as searching within the text) and easy portability make e-text popular. Hand-held computers (such as Personal Digital Assistants (PDAs)) allow a large number of e-texts to be carried. These devices also allow the e-text to be read on the move more conveniently than text printed on paper.
Project Gutenberg and other various digital libraries are using e-text.