Drawing and text output require a surface on which to draw. This surface is created by the DrvEnableSurface function and is referred to as the primary surface. This surface is also known as the on-screen surface, because it appears in the video display. There is only one primary surface enabled per PDEV although a driver can support several PDEVs. Drivers that support the DrvCreateDeviceBitmap function can create and use additional surfaces. These bitmap surfaces are referred to as secondary surfaces or off-screen surfaces. For either type of surface, the driver is responsible for determining the type of drawing operations it supports.