The screen size environment declaration defines the number of horizontal and vertical coordinate positions into which the screen is divided. This statement is optional. If you do not specify it in a windowed application, the screen defaults to the resolution of the display.

If you define a screen size, you must do so at the beginning of the program. You cannot define more than one screen size per program, and the size, whether specifically defined or defined by default, cannot be changed during runtime.

You can divide a screen into any number of logical horizontal and vertical positions. Once the screen size has been established, it can be thought of as a two-dimensional grid of X (horizontal) and Y (vertical) coordinates in which all objects are placed. Object positions (every object must have a specified position) are within these coordinates. Any objects positioned outside of the coordinates specified by the screen size declaration will not be displayed.