Vi editor

The Vi text editor is a screen editor written by CSRG at Berkeley. Its inclusion in the BSD UNIX distributions has made it popular.

It was inspired by EMACS, but differs from that it in is 'moded' (i.e. in one mode, characters typed on the keyboard are inserted into the buffer; in the other, they are interpreted as commands - for motion of the on-screen cursor, editing, file actions, etc).