More precisely this refers to the bits allocated per pixel (thus depth) for a display device. The actual use of the bits per pixel may vary depending on the desired goal. Commonly 8 bits per pixel allows the value for the pixel to be referenced to a lookup table of 256 different preset colors, however other times the bits are simply used to generate a monochrome value for the pixel ranging from 0 to 255 representing intensity. In contrast, 24 bits per pixel allocates 8 bits for the red, green, and blue value of each pixel. With small bit depths, bit packing tends to occur, such that multiple pixels are packed into a single byte. This may require the use of a combination of logical operations to insert the desired bits into the byte for a single pixel without disturbing the others, yielding a tradeoff between size and speed.