In telecommunication, the term landscape mode has the following meanings:

  1. In facsimile, the mode for scanning lines across the longer dimension of a rectangular object, i.e., rectangular original.
  2. In computer graphics, the orientation of an image in which the longer dimension is horizontal.
  3. An orientation of printed text on a page such that the lines of text are parallel to the long dimension of the page.
Note: If the page contains an image, such as a picture, and the page is viewed in the normal manner, the long dimension of the page would be parallel to the line that joins the eyes of the viewer.

Source: from Federal Standard 1037C