How GDI/GDI+ works without OpenGL or DirectX

Sorry if this is off-topic here. If so; please feel free to move it to the appropriate site.
How does GDI/GDI+ render to the graphics card (display content on the screen) without the use of a lower-level API for communicating with the GPU such as DirectX or OpenGL? How does it draw to the screen without the use of either API? Yes; I know that the image is composited and rendered on the CPU, but then it SOMEHOW has to be sent to the GPU before being displayed on the monitor. How does this work?