WindowSize

WindowSize is an option for notebooks that determines the size of the window in which the notebook is displayed.

WindowSize w, h gives the width and height of the window in printer's points, where 72 points equal one inch.

Setting either the width or height to Automatic causes the size of the window to be determined from the setting for WindowMargins and the size of your screen.

The setting for WindowSize changes whenever you resize a window interactively in the front end.

On most computer systems, the front end does not allow window sizes below a certain minimum value.

See The Mathematica Book: Section 2.11.2 and Section 2.11.13.

See also: WindowMargins.