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A text editor is software application used for editing plain text. It is distinguished from a word processor in that it does not manage document formatting or other features commonly used in desktop publishing.
Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code.
Some text editors are small and simple, while others offer a broad and complex range of functionality. For example, Unix and Unix-like operating systems have the vi editor (or a variant), but many also include the Emacs editor. Microsoft Windows systems come with the very simple Notepad, though many people (especially programmers) use a more complete program. Under Apple Macintosh's classic Mac OS, there was the native SimpleText, which was replaced by TextEdit. Some editors, such as WordStar, have dual operating modes, allowing them to be either a text editor or a word processor.
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History
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Before text editors existed, computer text was punched into Hollerith cards with keypunch machines. The text was carried as a physical box of these thin cardboard cards, and read into a card-reader.
The first text editors were line editors oriented on typewriter style terminals and they did not provide a window or screen-oriented display. They usually had very short commands (to minimize typing) that reproduced the current line. Among them were a command to print a selected section(s) of the file on the typewriter (or printer) in case of necessity. An "edit cursor", an imaginary insertion point, can be moved by special commands that operated with line numbers of specific text strings (context). Later, the context strings were extended to regular expressions. To see the changes, the file needed to be printed on the printer. These "line-based text editors" were considered revolutionary improvements over keypunch machines. In cases typewriter-based terminals were not available, they were adapted to keypunch equipment. In this case the user needed to punch the commands into the separate deck of cards and feed them into the computer in order to edit the file.
When computer terminals with video screens became inexpensive, screen-based text editors became common. One of the earliest "full screen" editors is vi, which is still a standard editor for Unix and Linux operating systems. The productivity of editing using these editors (compared to the line-based editors) motivated many of the early purchases of video terminals.
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Types of text editors
Text editors geared for professional computer users place no limit on the size of the file being opened. In particular, they start quickly even when editing large files, and can edit files that are too large to fit the computer's main memory. Simpler text editors often just read files in an array in RAM. On larger files, this is slow, and very large files often do not fit.
The ability to read and write very large files is needed by many professional computer users. For example, system administrators may need to read long log files. Programmers may need to change large source code, or examine naturally large texts, such as an entire dictionary placed in a single file.
Some text editors include specialized computer languages to customize the editor (programmable editors). For example, Emacs can be customized by programming in Lisp. These usually permit the editor to simulate the keystroke combinations and features of other editors, so that users don't have to learn the native command combinations.
Another important group of programmable editors use REXX as their scripting language. These editors permit entering both commands and REXX statements directly in the command line at the bottom of the screen (can be hidden and activated by a keystroke). These editors are usually referred to as "orthodox editors", and most representatives of this class are derivatives of Xedit, IBM's editor for VM/CMS. Among them are THE, Kedit, SlickEdit, X2, Uni-edit and Sedit. Some vi derivatives such as vim also support folding as well as macro languages, and have a command line at the bottom for entering commands. They can be considered as another branch of orthodox editors family.
Many text editors for software developers include source code syntax highlighting and automatic completion to make programs easier to read and write. Programming editors often permit one to select the name of a subprogram or variable, and then jump to its definition and back. Often an auxiliary utility like ctags is used to locate the definitions.
Some editors include special features and extra functions, for instance,
Source code editors are text editors with additional functionality to facilitate the production of source code. These often feature user-programmable syntax highlighting, and coding tools or keyboard macros similar to an HTML editor (see below).
Folding editors. This subclass includes so-called "orthodox editors" that are derivatives of Xedit. The specialized version of folding is usually called outlining (see below).
HTML editors are basic text editors with extra functionality for the manipulation and previewing of code, typically of programming languages used for web development. The additional functionality may include syntax highlighting, and usually includes wizards, toolbars or keyboard macros, or a combination of these.
Outliners. Folding (see above) can generally be considered a generalized form of outlining.
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See also
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