In a raster-scan program, the electron ray is swept across the monitor, just one strip at any given time from best to bottom level. Seeing that the electron ray strikes across each and every row, the ray power is started up and off to create a pattern of illuminated spots. Picture definition is stored in a memory area called the refresh buffer or frame buffer. This memory area holds the set of intensity values for all the screen points. Stored intensity values are then retrieved from the refresh buffer and “Painted” on the screen one row (scan line) at a time. Each screen point is referred to as a pixel or pel (shortened forms of picture element).