vi – a one of the most common text editors on Unix. It was developed starting around 1976 by Bill Joy at UCB, who was tired of the ed editor. But since he used ed as a code base, access to the original sources has required a commercial Unix Source Code License for more than twenty years. In January 2002, Caldera was so kind to remove usage restrictions to the Ancient Unix Code by a BSD-style license and thus vi is now finally free.
Compared to most of its many clones, the traditional vi is a rather small program (the binary size is approximately 160 kBytes on i386) just with its extremely powerful editing interface, but lacking fancy features like multiple undo, multiple screens, or syntax highlighting.
This port of vi has generally preserved the original style, terminal control, and feature set. It adds support for international character sets, including multibyte encodings such as UTF-8, and some minor enhancements that were not present in BSD vi 3.7, but had been included in later vi versions for System V or in POSIX.2.
The name “vi” is derived from the shortest unambiguous abbreviation for the ex command visual, which switches the ex line editor to its full-screen mode.
The vi screenshot source: Wikipedia; author: Huihermit; License: Creative Commons CC0 1.0 Universal Public Domain Dedication.