a frame buffer may be designed with enough memory to store two frames worth of video data. in a technique known generally as double buffering or more specifically as page flipping, the framebuffer uses half of its memory to display the current frame. while that memory is being displayed, the other half of memory is filled with data for the next frame. once the secondary buffer is filled, the framebuffer is instructed to display the secondary buffer instead. the primary buffer becomes the secondary buffer, and the secondary buffer becomes the primary. this switch is often done after the vertical blanking interval to avoid screen tearing where half the old frame and half the new frame is shown together.