- J key is used for going downward (like down arrow key)
- K key is used for going upward (like up arrow key)
- H key is used for going towards left (like left arrow key)
- L key is used for going towards right (like right arrow key)
You might have wondered that while arrow keys are available, why this odd set of keys can also be used for moving the cursor!
Well, the answer lies in the old days of computing. Bill Joy was a programmer who, in 1976, created a text editor for programmers. He named it “vi” and it runs on Linux/Unix platform… vi is still a very popular text editor among programmers.
Bill Joy used an ADM-3A terminal computer to design vi. This terminal did not have any arrow keys in its keyboard. So, Bill assigned J,K, H and L keys for directional navigation. These keys were to be used in combination with CTRL key. Although now it would be almost impossible to find a keyboard without arrow keys –but the legacy is still going on. The same scheme of JKHL is followed in modern versions of vi editor.
Because most of the engineers working in Google and other such bigshot online companies have trained on Linux platform and they abundantly use vi editor –the scheme of J, K, H and L keys is still surviving on keyboards and programs. For programmers this set of keys is very natural for cursor movement –but to lay people it definitely sounds curious. And now you've also known the secret behind it!