The display manager, like the trace manager, is designed to conceal implementation details from the applications programmer. It consists of two calls: one for delivering a trace to the display manager for plotting, and another to inform the display manager that the image is complete. Each instance of the display manager buffers images until a signal from the user interface notifies it to copy or assemble an image in video memory and display it. This interface with the application allows the user to have complete control over what is displayed and the movie display rate.