QUESTION 3:
(Review:) Is there a difference between the memory used to hold programs and the memory used to hold data?
No. The various devices must cooperate somehow so their data and signals don't get mixed.
The way devices connected to a bus cooperate is another facet of a bus standard.
Input/output controllers receive input and output requests from the central processor, and then send device-specific control signals to the device they control. They also manage the data flow to and from the device. This frees the central processor from involvment with the details of controlling each device. I/O controllers are needed only for those I/O devices that are part of the system.
Often the I/O controllers are part of the electronics on the main circuit board (the mother board) of the computer. Sometimes an uncommon device requires its own controller which must be plugged into a connector (an expansion slot) on the mother board.
(Review:) Is there a difference between the memory used to hold programs and the memory used to hold data?