Screen editor

A screen editor (sometimes called a 'video editor', but not to be confused with modern applications used for editing videos) is a text editor which used a video terminal for an early form of WYSIWYG user interface, one in which the user saw the current contents of the file they were editing on the screen, which changed as each character was typed on the keyboard.

Although they were computationally more expensive (since the editor process generally had to be woken up as each character was typed), they were so superior in ease of use, to existing editors (all designed for printing terminals), that they spread rapidly.

Among the first screen editors (perhaps the first?) were the Emacs editors, but others (such as the vi editor) soon followed.