In order to easily use a monochrome type PC monitor with an 8051 you will also need to mate a Monochrome Video Adapter board to the 8051. The output of this board can then drive the monitor. The interface of the video adapter will be very similar to the process to connect a color video board (CGA, EGA, or VGA) to an 8051. The subject of the CGA board was recently discussed in detail on this message board. Do a search for CGA to find it.
Michael Karas