Why Does Vim Use H J K L? The Surprising History Behind vi’s Quirky Design

1. The Early Days of vi

In the fall of 1975, Ken Thompson returned to Berkeley with a Unix system on a PDP‑11/70 and wrote a Pascal compiler. Bill Joy, then a student, discovered bugs in that compiler and began hacking it. At the time, no IDE existed; programmers used the line editor ed , also created by Thompson.

Ed was cumbersome, leading to a series of successors— em , en , eo , ep —and finally ex , a line editor that introduced a visual mode. Bill Joy refined ex into vi , the visual interface that became famous.

Unlike modern editors, these early tools lacked a cursor; they operated on whole lines, which made editing feel unintuitive to newcomers.

Example: correcting a typo in a two‑line file.

1
hello wold !
s/wold/world
1
hello world !

This illustrates the cumbersome, line‑oriented workflow that vi later streamlined.

2. Keyboard Layout and Mode Switching

The ADM‑3A terminal, which Berkeley later acquired, had no dedicated arrow keys. Consequently, the letters H, J, K, and L were repurposed to move the cursor left, down, up, and right.

Additionally, the Esc key shared the same position as today’s Tab key, allowing users to switch between command and insert modes without moving their left hand.

These quirks persisted even after keyboards evolved, because users had grown accustomed to them.

3. vi’s Command Language

vi separates editing into verbs (actions) and nouns (text objects), optionally modified by prepositions that define scope.

d : delete

r : replace

y : yank (copy)

v : visual select

Nouns describe what is being edited:

w : word

s : sentence

p : paragraph

Modifiers (sometimes called prepositions) specify the range:

i : inside (e.g., diw deletes the word under the cursor)

a : around (e.g., daW deletes a word plus surrounding whitespace)

t : till (up to but not including a character)

f : find (up to and including a character)

Combining them yields expressive commands such as: diw – delete inside word cis – change inside sentence dte – delete till ‘e’ vis – visual select inside sentence

Because vi was written for 300‑baud modems, its design emphasizes minimal keystrokes and mode‑based operation, a philosophy that still influences modern Vim users.

Understanding this history explains why vi’s seemingly odd key bindings and modal workflow persist and why mastering them unlocks a powerful, efficient editing environment.