Semigraphics

Text-based semigraphics or pseudographics is a primitive method used in early text mode video hardware to emulate raster graphics without having to implement the logic for such a display mode.

There are two different ways to accomplish the emulation of a raster graphics. The first one is to create a low-resolution all-points-addressable mode using a set of special characters with all binary combinations of a certain subdivision matrix of the text mode character size; this method referred to as block graphics, or sometimes mosaic graphics.