So you discover that in 16-bit real mode, the BIOS handles hardware directly and your OS doesn't need device drivers. Sweet! Freedom from driver hell, right? Then you learn about 16-bit memory segmentation and suddenly that smile disappears faster than your will to live. For the uninitiated: in real mode, memory addresses are calculated using segment:offset pairs, and because both are 16-bit values, segments can overlap in the most cursed ways possible. You can have multiple segment:offset combinations pointing to the same physical address. It's like having 5 different street addresses for the same house, except the mailman is your CPU and it's having an existential crisis. Suddenly writing device drivers doesn't seem so bad anymore. At least those make logical sense. Overlapping segments? That's just sadism with extra steps.