Line editor
Encyclopedia
A line editor is a text editor
Text editor
A text editor is a type of program used for editing plain text files.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....

 computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

 that manipulates text primarily by the display, modification, and movement of lines. Line editors precede screen-based text editors and originated in an era when a computer operator typically interacted with a teleprinter
Teleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...

 (essentially a printer
Computer printer
In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...

 with a keyboard
Computer keyboard
In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...

), with no video display, and no ability to navigate a cursor interactively in a document. Line editors were also a feature of many home computers, avoiding the need for a more memory-intensive full-screen editor.

Line editors are limited to primitive text-oriented input and output methods. Most edits are a line-at-a-time. Typing, editing, and document display do not occur simultaneously. Typically, typing does not enter text directly into the document. Instead, users modify the document text by entering terse commands on a text-only terminal. Commands and text, and corresponding output from the editor, will scroll up from the bottom of the screen in the order that they are entered or printed to the screen. Although the commands typically indicate the line(s) they modify, displaying the edited text within the context of larger portions of the document requires a separate command.
Line editors keep a reference to the 'current line' to which the entered commands usually are applied. In contrast, modern screen based editors allow the user to interactively and directly navigate, select, and modify portions of the document. Generally line numbers or a search based context (especially when making changes within lines) are used to specify which part of the document is to be edited or displayed.

Early line editors included TECO
Text Editor and Corrector
TECO is a text editor originally developed at the Massachusetts Institute of Technology in the 1960s, after which it was modified by 'just about everybody'...

 and QED
QED (text editor)
QED is a line-oriented computer text editor that was developed by Butler Lampson and L. Peter Deutsch for the Berkeley Timesharing System running on the SDS 940. It was implemented by L...

, both dating back to pre-UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 era OSes. Emacs
Emacs
Emacs is a class of text editors, usually characterized by their extensibility. GNU Emacs has over 1,000 commands. It also allows the user to combine these commands into macros to automate work.Development began in the mid-1970s and continues actively...

 grew out of a set of macros written for TECO
Text Editor and Corrector
TECO is a text editor originally developed at the Massachusetts Institute of Technology in the 1960s, after which it was modified by 'just about everybody'...

.
The UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 editor ed is a classic example of a line editor. A line editor for DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...

 is Edlin
Edlin
Edlin is a line editor included with MS-DOS and later Microsoft operating systems. It provides rudimentary capabilities for editing plain text files through a command-driven interface. Line numbers are specified using numerals, and operations are specified using single-character alphabetic...

.

Line editors are still used non-interactively in shell script
Shell script
A shell script is a script written for the shell, or command line interpreter, of an operating system. It is often considered a simple domain-specific programming language...

s. Patch systems such as patch (Unix)
Patch (Unix)
patch is a Unix program that updates text files according to instructions contained in a separate file, called a patch file. The patch file is a text file that consists of a list of differences and is produced by running the related diff program with the original and updated file as arguments...

 traditionally used diff
Diff
In computing, diff is a file comparison utility that outputs the differences between two files. It is typically used to show the changes between one version of a file and a former version of the same file. Diff displays the changes made per line for text files. Modern implementations also...

 data that was a script of ed commands. They are also used in many MUD
MUD
A MUD , pronounced , is a multiplayer real-time virtual world, with the term usually referring to text-based instances of these. MUDs combine elements of role-playing games, hack and slash, player versus player, interactive fiction, and online chat...

 systems, though many people prefer to edit text on their own computer and then use their MUD client's upload feature to paste the text directly in the line editor. Perhaps the most widely-used line editors today are those contained in single-line input fields of modern GUI
Gui
Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...

s such as a web browser's location bar or HTML form elements.

See also

  • TECO
    Text Editor and Corrector
    TECO is a text editor originally developed at the Massachusetts Institute of Technology in the 1960s, after which it was modified by 'just about everybody'...

  • QED (text editor)
    QED (text editor)
    QED is a line-oriented computer text editor that was developed by Butler Lampson and L. Peter Deutsch for the Berkeley Timesharing System running on the SDS 940. It was implemented by L...

  • Visual editor
    Visual editor
    Visual editors or full screen editors are editing programs which display the text being edited on the screen as it is being edited, as opposed to line-oriented editors ....

  • ed
    Ed (text editor)
    ed is a line editor for the Unix operating system. It was one of the first end-user programs hosted on the system and has been standard in Unix-based systems ever since. ed was originally written in PDP-11/20 assembler by Ken Thompson in 1971...

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