Their kernel was open to SW devs since the very beginning, it's one of the reason that helped Windows grew in popularity especially as a video game platform. Ea

Their kernel was open to SW devs since the very beginning, it's one of the reason that helped Windows grew in popularity especially as a video game platform. Early 3d games needed direct kernel access to extract maximum performance from the HW, but then MS built Direct3D as a wrapper for that direct HW access so games couldn't crash your whole system.