Visual editor

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A visual editor, or full-screen editor is computer software for editing text files using a textual or graphical user interface which displays the content (text) in an easy to look at and good view; that is, it displays a portion of the opened file and updates it in real time. By definition, all visual editors require a re-fresh-able display device and all editors with a GUI are visual. Editors that are running through a command-line interpreter, however, may or may not be.

Before the widespread use of glass monitors, computers used display devices that printed on paper (for example, the IBM 2741, a modified Selectric typewriter). As paper is not refreshable, software had to be designed with certain restrictions in mind. Programs could either be set-and-forget (i.e., take arguments at startup with no further input) or command-line interpreters specialized for a particular task. Furthermore, the data storage methods available at the time dictated that text editors operated either on a continuous spool of paper tape containing the entire document, the basic unit of which was the byte, or on a physical stack of punched cards, each holding a line of up to eighty characters, the basic unit of which was the card. Although storage and display methods advanced over time, the metaphors remained the same; "punched cards" (later virtual) could be inserted, removed, and shuffled around, while "tape" was read up to the next page break and edited by moving it a character, word, line, or page forwards or backwards, or by searching for a pattern.

The Tape Editor and Corrector originally ran on the Digital Equipment Corporation PDP-1, a tape-based, single-user machine; it was appropriately character-oriented, and could run either "offline" (set-and-forget, to save computer time) or interactively as a REPL (to prevent mistakes). IBM mainframes, on the other hand, used punched cards and supported multiple users; accordingly, their editors were all line-oriented and interactive. The SDS 940 had a hard disk drive; its editor, QED, was line-oriented. Computers running Unix, Linux, and BSD have a selection of line editors: ed for interactive use, sed for offline use, and ex, an 'extension to ed.

When glass monitors came into use, editors were upgraded to take advantage of their features, while continuing to use the old syntax as far as possible. TECO got a video mode on the PDP-6; this later served as an inspiration for SciTECO. Its unparalleled macro capabilities led to the development of a very different editor: Emacs, originally an effort to standardize the editor mac'ros in use at the Massachusetts Institute of Technology. PDP-1 TECO is a character editor, while PDP-6 TECO, SciTECO, and Emacs are visual editors. Likewise, Unix ex was combined with em (the Editor for Mortals) to create vi; vi and ex are the same program running as a visual and line-oriented editor, respectively. These are all advanced editors, requiring a considerable amount of training in their use. When the University of Washington wished to create an e-mail client for novice users, a simpler editor was needed; the result was pico, and---due to legal issues---nano.



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