Visual editor

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 . 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.

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