Hercules Graphics Card (HGC) is a computer graphics controller, widely used from the mid 1980s. It was common on IBM compatible PCs connected to a monochrome (green, amber or, less often, black-white) phosphor monitor. It supported a single graphics mode: 720 x 348 pixels at 1 bit per pixel.
Hercules card has certain popularity, especially in specialist applications, such as some Debuggers and CAD programs. Because it's graphic page was hardwired to address '0b000h' instead of address '0a000h' in newer (color) graphic adapters. Therefore a HGC was connectable along side another graphic adapter with fewer problems. Certain software detected a HGC connected to a secondary monitor, and used the mono display for extra data while running the application on the other display.
