in vga graphics boards, the digital color information stored in the video memory (4 bits for 16 colors or 8 bits for 256 colors) is converted into a digital 18- bit value in the graphics adapter in a clut (colorlookuptable). the 3 x 6 bits are converted separately for r/g/b (red/green/blue) in the ramdac (d/a converter) and transferred to the monitor as analog signals on just three lines (plus sync lines). the original color values are converted into completely different values by means of a translation table. the value stored in the video memory is thus not a color value, but only a pointer to a table in which the actual color value is found. the advantage of this method: only 8 bits need to be stored for each pixel, although the color values are 18 bits wide; the disadvantage: only 256 colors can be displayed simultaneously from a palette of 262,144 possible colors.