OVERSTRIKE MODE

  Sets the mode of the current buffer to overstrike, as opposed to insert.
  As you type, the new text replaces existing text at the current position
  ---hence, overstrike mode is sometimes called "replace mode" or "type-over
  mode."

  Usage notes:

  o  The mode of the buffer is shown in the status line. It also affects
     some commands and keys such as DELETE, ERASE CHARACTER, and RESTORE
     CHARACTER.

  o  If you use SET BOX NOPAD, the mode of the buffer affects box editing.
     In overstrike mode, cutting a box, pads the area with spaces to keep
     the column alignment of text to the right of the box, and pasting a box
     overwrites existing text. To override these effects without changing
     your settings, use BOX CUT INSERT and BOX PASTE INSERT.

  o  If your system has a mouse, you can toggle the mode of the buffer by
     clicking M1 on the Insert or Overstrike indicator in the status line.
     This works on DECwindows, DECterm, or UIS. See help on Status Line.

  Related topics:

     Status Line     CHANGE MODE     INSERT MODE     SET BOX NOPAD