hjkl Were the Arrow Keys

You move with h j k l because your hands never leave the home row. That is the usual explanation. But why those four? Plenty of other keys sit on the home row.

In the mid-1970s Bill Joy wrote vi on a Lear-Siegler ADM-3A. That terminal had no arrow keys. Instead, the arrows were printed on the faces of H, J, K and L. So he was using the arrow keys all along. They just happened to sit under his right hand.

The terminal is long gone. The engraving stayed, and fifty years later it is still under your fingers.