Programming in lower level

Sometimes a control engineer may want to make computers to give commands to or read measurements from machines.
Understanding how computers work under the hood would be helpful in such situations.

Chinese Room

Assume a person inside of a closed room with slots for questions and answers.
From outside, a person would (in)put a letter with a question in an unfamiliar foreign language into the room.
The person inside of the room has a very big book with answers to all questions of that foreign language.
The person inside of the room would lookup the answer from the book and (out)put another letter in the foreign language with the answer out of the room.
Now, do people outside of the room can tell if the person inside knows the foreign language?

thought experiment	computer
room	CPU
person inside of the room	CPU electronics
book in the room	CPU instruction set
people outside of the room	memory
letter coming in	machine language instruction
letter going out	result of the machine language instruction
frequency of letter	clock speed

memory	physical location	amount	speed	purpose
registers	CPU	very limited	fastest	operation, addressing, I/O
cache	In or close to CPU	not much	faster	accelerating information fetching
main memory	motherboard RAM	GBs nowadays	fast	store code and data
stack	within RAM	limited	RAM	store function call information
heap	within RAM	less limited	RAM	allocate memory from here
SSD	SSD	TBs?	Flash memory speed	preserve code and data
HDD	HDD	TBs	Magnetic disk speed	preserve code and data
Memory mapped I/O	???	limited	???	communicate with a device

Among these memories, cache is usually not accessable from the program.
Disk drives, programs can access through file systems.
Main memory (+ stack and heap) is addressable; thus we can use pointers to access.
How to access registers depends on the compilers.
Memory mapped IO is addressable; thus we can use pointers to access. However, if output, the computer would send what we write here to a device, possibly an external one.