In the following example, the default window is assigned to the temporary variable drawable. A graphics context called gc is created for this drawable with no initial values. Notice that the CgConstants pool dictionary constant None is used to indicate that no values are being set. In the next line, the foreground color is set to black. (The blackPixel message, used to get the pixel value for black, is discussed in "Drawing in black and white".) The drawable is then sent a message to draw a filled rectangle at the appropriate coordinates using the display attributes from the graphics context called gc. At the end of this routine, the GC is freed, and its resources are returned to the operating system.