A Windows application has access to a large and varied set of device-independent graphics operations. This means your application can easily draw lines, rectangles, circles, and complex regions. Because Windows provides device independence, applications can use the same functions to draw a circle on either a dot-matrix printer or a high-resolution graphics screen.
Windows requires device drivers to convert graphics-output requests to output for a printer, plotter, screen, or other output device. A device driver is a special executable library that an application can load and connect to a specific output device and port. A device context represents the device driver, the output device, and perhaps the communications port. Your application carries out graphics operations within the context of a specific device.