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he purpose of using plain text today is primarily a "lowest common denominator" independence from programs that require their very own special encoding or formatting (with due sacrifices and limitations). Plain text files can be opened, read, and edited with most text editors. Examples include Notepad (Windows), edit (DOS), ed, vi or vim (Unix, Linux), SimpleText (Mac OS), or TextEdit (Mac OS X). Other computer programs are also capable of reading and importing plain text. It can also be used by simple computer tools such as line printing text commands like type (DOS and Windows) and cat (Unix).Plain text files are almost universal in programming; a source code file containing instructions in a programming language is almost always a plain text file. Plain text is also commonly used for configuration files, who were read for saved settings at the startup of a program.
[edit] Related terms
The related term, plaintext, is most commonly used in a cryptographic context, while cleartext usually refers to lack of protection from eavesdropping. Usage of these terms is such that there is some confusion amongst them, especially among those new to computers, cryptography, or data communications.
[edit] Philosophy
This reveals that plain text is in fact the technical user's way to regard a file or a sequence of bytes. In this sense, there is no plain text, since bits are stored as states of latches, charges on transistor gates, microscopic magnetic or mechanical dots on a disk, etc, and humans don't have the senses needed to read this. The information must thus appear as text (on screen or on paper) in order to be text in this absolute sense of the word.
Plain text is a way to represent generic text without attributes such as fonts, subscripts, and boldface; due to this simplicity, it is readable and processable by almost any computer program. In a way a HTML, SGML and an XML file is regarded as plain text, since no control codes (see below) are used, but real structural tags are actually included in these formats. As regards to the SGML and XML author, these tags are "human readable" since that format author understands the structure by reading the format. This may illuminate the complications of the usage of terms within computer science: it's all a relative view point.
[edit] Encoding
[edit] Character encodings
Main article: character encoding
Text was once commonly encoded in ASCII, using 8 bits for one letter or other character, encoding 7 bits, allowing 128 values, and using the 8th as a checksum bit when transferring a file. This just allowed the ordinary Latin alphabet, transfer control codes, parentheses and interpunction, which annoyed especially Portuguese and Swedish[citation needed] computer users. Therefore, when data transfer became more stable, the remaining 128 values were encoded, everywhere differently, and in a way that made multilingual texts impossible to encode. At last Unicode was defined, which currently allows for 1,114,112 code values used for any modern text writing system, and a lot of extinct ones. For example Unicode codes Chinese, Hebrew, Cyrillic as well as Latin. Some of these text formats may be pretty complicated to process correctly, but they still contain no structural data, such as bold start and end markers, and are therefore plain text.
[edit] Control codes
Main article: newline
The ASCII codes before SPACE (= 32 = 20H) are not intended as displayable characters, but instead as control characters. They are used for a diversity of interpreted meanings, for example the code NULL (= 0, sometimes denoted Ctrl-@) is used as string end markers in the programming language C and successors. Most troublesome of these are the codes LF (= LINE FEED = 10 = 0AH) and CR (= CARRIAGE RETURN = 13 = 0DH). Windows and OS/2 require the sequence CR,LF to represent a newline, while Unix and relatives use just the LF, and Classic Mac OS (but not Mac OS X) uses just the code CR. This was once a slight problem when transferring files between Windows and Unices, but today most computer programs treat this seamlessly.
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"Humanitarianism is the expression of stupidity and cowardice."- Adolf Hitler
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