Text editor

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For the use of text editors with Wikipedia, see Wikipedia:Text editor support.
An example of a text editor, Leafpad

A text editor is a type of program used for editing plain text files.

Text editors are often provided with operating systems and software development packages, and can be used to change, e.g., configuration files, documentation files, programming language source code.

Plain text files vs. word processor files[edit]

There are important differences between plain text files created by a text editor and document files created by word processors such as Pages,[importance?] Microsoft Word, and WordPerfect.

Word processors were developed to allow formatting of text for presentation on a printed page, while text produced by text editors is generally used for other purposes, such as input data for a computer program.

When both formats are available, the user must select with care. Saving a plain text file in a word-processor format adds formatting information that can make the text unreadable by a program that expects plain text. Conversely, saving a word-processor document as plain text removes any formatting information.

History[edit]

A box of punched cards with several program decks.

Before text editors existed, computer text was punched into cards with keypunch machines. Physical boxes of these thin cardboard cards were then inserted into a card-reader. Magnetic tape and disk "card-image" files created from such card decks often had no line-separation characters at all, and assumed fixed-length 80-character records. An alternative to cards was punched paper tape. It could be created by some teleprinters (such as the Teletype), which used special characters to indicate ends of records.

The first text editors were "line editors" oriented to teleprinter- or typewriter-style terminals without displays. Commands (often a single keystroke) effected edits to a file at an imaginary insertion point called the "cursor". Edits were verified by typing a command to print a small section of the file, and periodically by printing the entire file. In some line editors, the cursor could be moved by commands that specified the line number in the file, text strings (context) for which to search, and eventually regular expressions. Line editors were major improvements over keypunching. Some line editors could be used by keypunch; editing commands could be taken from a deck of cards and applied to a specified file.

When computer terminals with video screens became available, screen-based text editors (sometimes called just "screen editors") became common. One of the earliest full-screen editors was O26, which was written for the operator console of the CDC 6000 series computers in 1967. Another early full-screen editor was vi. Written in the 1970s, it is still a standard editor[1] on Unix and Linux operating systems. Emacs, one of the first open source and free software projects, is another early full-screen or real-time editor, one that was ported to many systems.[2] A full-screen editor's ease-of-use and speed (compared to the line-based editors) motivated many early purchases of video terminals.[3]

Types of text editors[edit]

Emacs, a text editor popular among programmers, running on Microsoft Windows

Some text editors are small and simple, while others offer broad and complex functions. For example, Unix and Unix-like operating systems have the pico editor (or a variant), but many also include the Emacs editor. Microsoft Windows systems come with the simple Notepad, though many people—especially programmers—prefer other editors with more features. Under Apple Macintosh's classic Mac OS there was the native SimpleText, which was replaced in Mac OS X by TextEdit, which combines features of a text editor with those typical of a word processor such as rulers, margins and multiple font selection. Most word processors can read and write files in plain text format, allowing them to open files saved from text editor. Saving these files from a word processor, however, requires ensuring the file is written in plain text format, and that any text encoding or BOM settings won't obscure the file for its intended use. Non-WYSIWYG word processors, such as WordStar, are more easily pressed into service as text editors, and in fact were commonly used as such during the 1980s. Later word processors like Microsoft Word are almost never used to edit plain text files.

Text editors for professional users can edit files of arbitrary sizes, such as log files or unusually large texts, such as an entire dictionary placed in a single file. Simpler text editors may just read files into the computer's main memory. With larger files, this may be a slow process, and the entire file may not fit. Some text editors do not let the user start editing until this read-in is complete.

"Programmable editors" can be customized for specific uses. For example, Emacs can be customized by programming in Lisp. One motive for customizing is to make a text editor use the commands of another text editor with which the user is more familiar. The programming environments of many text editors are limited to enhancing the core functionality of the program, but editors such as Emacs can be extended almost without limit—for web browsing, reading email, online chat, managing files or playing games.

An important group of programmable editors uses REXX as a[4] scripting language. These "orthodox editors" contain a "command line" into which commands and macros can be typed and a line number or sequence filed into which line commands or macros can be typed. Most such editors are derivatives of ISPF/PDF EDIT or of XEDIT, IBM's flagship editor for VM/CMS. Among them are THE, KEDIT, SlickEdit, X2, Uni-edit, UltraEdit, and SEDIT. Some vi derivatives such as Vim also support folding as well as macro languages, and also have a command line.

A text editor written or customized for a specific use can sense what the user is editing and assist the user, often by providing simple ways to retrieve related information. 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 let the user select the name of a subprogram or variable, then jump to its definition and back. Often an auxiliary utility like ctags is used to locate the definitions.

Typical features[edit]

Specialised editors[edit]

Some editors include special features and extra functions, for instance,

See also[edit]

Notes[edit]

  1. ^ "The Open Group Base Specifications Issue 6, IEEE Std 1003.1, 2004 Edition". The IEEE and The Open Group. 2004. Retrieved January 18, 2010. 
  2. ^ "Introducing the Emacs editing environment". 
  3. ^ "Multics Emacs: The History, Design and Implementation". "Some Multics users purchased these terminals ..., using them either as "glass teletypes" or via "local editing."" 
  4. ^ Originally macros were written in assembler, CLIST (TSO), EXEC (VM), EXEC2 (VM) or PL/I, but most users dropped CLIST, EXEC and EXEC2 once REXX was available.
  5. ^ LAPIS: Smart Editing with Text Structure
  6. ^ Lightweight Structured Text Processing
  7. ^ New gedit plugin: multi edit, and a demo video.

External links[edit]