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  Although the ROM BIOS services for the PC let you move the cursor anywhere
  on the screen and basically give you full-screen control, the standard DOS
  services do not. In fact, the DOS screen output services are completely
  oriented to "glass teletype" output--output that encompasses only what can
  be done with a printer. This, of course, ignores the richer potential of a
  display screen. This lack of full-screen output in DOS forces most
  programs to bypass the DOS services and use lower-level services, such as
  the ROM BIOS services.

  The screen control commands of the ANSI driver remedy this situation by
  providing a set of full-screen commands that can be used to do nearly
  anything that the display screen is capable of doing. The commands include
  moving the cursor, clearing the screen, setting the display attributes
  (color, underscore, blinking, and so on), and changing the mode from text
  to graphics and vice versa. As an additional level of sophistication, some
  commands can save the current cursor location so that you can move the
  cursor to display information and then return it to its original position.