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, could 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 case 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 available, screen-based text editors became common. One of the earliest "full screen" editors was O26 - which was written for the operator console of the CDC 6000 series machines in 1967. Another early full screen editor is vi. Written in the 1970s, vi is still a standard editor for Unix and Linux operating systems. The productivity of editing using full-screen editors (compared to the line-based editors) motivated many of the early purchases of video terminals.
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—prefer to use one of many other Windows text editors with more features. 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.
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 are capable of editing files that are too large to fit the computer's main memory. Simpler text editors often just read files into an array in RAM. On larger files this is a slow process, 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 files, or examine unusually 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 do not 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, UltraEdit, 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 another branch of the family of orthodox editors.
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.
Most text editors provide methods to duplicate and move text within the file, or between files.
As with word processors, text editors will provide a way to undo and redo the last edit. Often—especially with older text editors—there is only one level of edit history remembered and successively issuing the undo command will only "toggle" the last change. Modern or more complex editors usually provide a multiple level history such that issuing the undo command repeatedly will revert the document to successively older edits. A separate redo command will cycle the edits "forward" toward the most recent changes. The number of changes remembered depends upon the editor and is often configurable by the user.
Reading or merging the contents of another text file into the file currently being edited. Some text editors provide a way to insert the output of a command issued to the operating system's shell.
Some advanced text editors allow you to send all or sections of the file being edited to another utility and read the result back into the file in place of the lines being "filtered". This, for example, is useful for sorting a series of lines alphabetically or numerically, doing mathematical computations, and so on.
Some editors include special features and extra functions, for instance,
A text editor is a program that is run on a computer that can create and change text. The text can be saved into a file that is called a "text file". Text editors can be used for a lot of things. Many people use them to write up documents. Some people write code (like HTML or C++) using a text editor.
Some text editors can edit rich text. Rich text allows the person that is editing text to have bold text, italic text, and other things.
Most text editors today support search and replace. This means that the computer will quickly find some text the user wants, and allow them to replace it with some other text. This can be in part or all of the document.
Copy, cut and paste are other common options in text editors. Copy allows users to instantly add a copy of text in one place to another place. Cut and paste are similar, except that the text is moved from one place to another instead of being copied. This is very useful when a writer wishes to put his paragraphs in a different order, for example.
Sometimes users make mistakes, or need to do the same thing over and over without getting bored. This is what the undo and redo features do. Users can reverse their mistakes, or quickly repeat their actions. Some editors allow many mistakes in a row to be reversed; others allow only one or two.