How operating systems manages hardware?

Answer 1

OS's manage hardware by creating a uniform set of functions or operations that can be performed on various classes of devices (for instance read x bytes at address y from hard drive of any type).

These general functions rely on a layer of drivers that provide specific means to carry out operations on specific hardware. Drivers are usually provided by the manufacturers, but the OS must provide a way to load and use drivers, as well as detect the device and select an appropriate driver if several are available.