Final answer:
To set the size of a graphics window to 640 in width and 480 in height, the command varies depending on the environment. In Python's Pygame, it's done with 'pygame.display.set_mode((640, 480))'. For other libraries or languages, consult their respective documentation.
Step-by-step explanation:
The command you would use to specify a size for the graphics window, setting it to 640 for width and 480 for height, largely depends on the programming environment or the graphics library you are using. However, assuming the use of a common language like Python and a popular graphics library such as Pygame, the command would look like this:
screen = pygame.display.set_mode((640, 480))
In this Pygame command, pygame.display.set_mode() is used to initialize a window or screen for display. The argument (640, 480) represents the size of the window in pixels with 640 being the width and 480 the height.
If you're working with a different library or environment like Processing, Tkinter, or even a different language such as Java or C++, the command will be different. You will need to refer to the specific documentation for the environment you are using for the exact command.