The long and short of it
There are two approaches to hardware of today. First a little history is in order. Our Hardware systems of today conform to strict standards. In the early times (pre 1980) hardware used discrete components known as IC's transistors, resistors and capacitors. Hardware did not contain anything but the simplest built in control. There were no ROMS allowing easy interfacing. Each manufacturer gave a spec sheet on his device and if you wanted to use it you would need to develop a program that both satisfied the timing requirements and functional requirements for your purpose.
Today with the exception of Winmodems, our devices have well written programs called firmware that handle the real basics depicted above.