A Video Display Controller or VDC is an integrated circuit which is the main component in a video signal generator, a device responsible for the production of a TV video signal in a computing or game system. Some VDCs also generate an Audio signal, but in that case it's not their main function.
VDCs were most often used in the old home-computers of the 80s, but also in some early video game systems.
The VDC is always the main component of the video signal generator logic, but sometimes there are also other supporting chips used, such as RAM to hold the pixel data, ROM to hold character fonts, or perhaps some discrete logic such as shift registers were necessary to build a complete system. In any case, it's the VDC's responsibility to generate the timing of the necessary video signals, such as the horizontal and vertical synchronisation signals, and the blanking interval signal.
Most often the VDC chip is completely integrated in the logic of the main computer system, (its video RAM appears in the memory map of the main CPU), but sometimes it functions as a coprocessor that can manipulate the video RAM contents independently
Read more about Video Display Controller: Video Display Controllers Vs. Video Display Processors and Graphics Processing Units, Types of Video Display Controllers, List of Example VDCs, Alternatives To Using A VDC Chip, Later Solutions
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