A frame buffer is a portion of random-access memory (RAM) that contains a bitmap that drives a video display. It is a memory buffer containing data representing all the pixels in an image or video frame. The frame buffer is the region of memory that holds the color data for the image displayed on a computer screen. The picture is built up in the frame buffer one bit at a time, and each pixel in the frame buffer must be accessed and converted before it is visible on the raster CRT. A frame buffer can use a color buffer to hold the color data for an image, a depth buffer to hold a depth value for each pixel, and something called a stencil buffer. The term "frame buffer" is often used interchangeably when referring to the RAM on the video card where the bitmap of image data is "buffered" for display. 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.