The technical names for these programs are SO long that they are NEVER used.

Here is a description of them:
  One - Display the first screen of a file.

  Two - One, with scrolling.

  Three - showing only the first screen of the file, do basic 'blind' editing

  Four - showing only the first screenfull of information do editing with
           the ability to see the cursor.

  Five - four with ability to scroll.