All of the slots and plugs both inside and outside the computer case are shaped a certain way to accept a certain type of part. Some will not even accept parts even one generation behind, such as the CPU and memory. Others, like the video plug have not changed in years. Some of the plugs, such as the video, keyboard and mouse plugs, are a special color. These colors make it easier to pair the plug to the port. The motherboard is also may also be referred to as the PCB which stands for ‘printed circuit board’, though it is essentially a gigantic PCB and can be considered the 'primary' PCB.