In general, the term “bitmap” refers to an image formed by a pattern of bits, rather than by a pattern of lines. In Microsoft Windows, there are two kinds of bitmaps:
A “device-dependent” bitmap is a pattern of bits in memory which can be displayed on an output device. Because there is a close correlation between the bits in memory and the pixels on the display device, a memory bitmap is said to be device dependent. For such bitmaps, the way the bits are arranged in memory depends on the intended output device.
A “device-independent” bitmap (DIB) describes the actual appearance of an image, rather than the way that image is internally represented by a particular display device. Because this external definition can be applied to any display device, it is referred to as device independent.