Vi Turns 50: The True History of vi

Vi’s history begins with ed, Ken Thompson’s line-oriented UNIX editor, whose limitations frustrated Berkeley students working in 1975 to repair Thompson’s broken Pascal compiler. Bill Joy and Chuck Haley adapted ideas from EM, a more screen-oriented editor, into a sequence of tools that eventually became ex. Joy then built ex’s full-screen visual mode, vi, working from home over a 300-baud modem. Its terse, single-character commands helped make screen editing practical on such a slow connection, while its modes and controls also reflected the equipment available to its creator.

The ADM-3A terminal shaped vi’s most recognizable conventions: H, J, K, and L served as arrow keys, and Escape was conveniently placed for switching modes. Those choices persisted long after the hardware disappeared, illustrating how technical constraints can become lasting habits. Joy nearly added multiple windows and programmability, but lost the unfinished code when a tape drive failed and he had no backups, so he returned to the earlier version. Vi was released in 1979 in the second Berkeley Software Distribution and spread widely with UNIX, eventually becoming a POSIX standard. Its origins explain both its distinctive interface and its enduring reputation: a tool built for a vanished computing world remains a fixture on modern systems.