Operating system - basic computer structrue

1. Operating System
-Basic computer structure-
Junsoo kang

2. What is the computer?

3. Compute + er
..like this?

4. How about human? For compute

5. How about computer? For compute

6. Then how can we see that
result from computing?

7. So we prepared...
IO(input output) Devices!

8. I have a power to directly
direct all of my computer
devices!

9. Device
Controller
Device
Controller
Device
Controller
Device
Controller
Device
Controller
Device
Controller
Device
Controller

10. What is the program?

11. Program literaly means to do list
will be exacuted by CPU, And thy are storaged
type of file in secondary storage device

12. -But actually CPU does not work with program.. He really work with 'Process'.
-I said the CPU allways work with memory.
-But program just mean to do list not actually exacuted.
-Process means the program on the main memory which runned by user's input
mouse double cliking or using command line.

13. Actually We can play game with internet
surfing and listen music or even any
kind of program
We call this technique 'Multi process'

14. -IO processing is kind of very very slow work So computer use this time to process
change
-But lets think about a process it's very simple code with infinity loop and there is
no kind any IO processing
-There is no time to process changes. Then How can computer engineer solve it?
-The answer is Timer.
IO processing and process change

15. Check and set process
allocation cpu time!

16. IO devices
Timer
CPU
Main Memory

17. How can Timer notice to Cpu the process allocation time pasted?

18. How can Timer notice to Cpu the process allocation time pasted?
Interrupt!

19. What is the interrupt?

20. IO devices
Timer
CPU
Main Memory
Interrupt is simply kind of pulse signal

21. Interrupt is simply kind of pulse signal
IO Device to CPU
Process itself interrupt(trap)

22. IO devices
Timer
CPU
Case 1

23. IO devices
Timer
CPU
Case 2

24. Case 2
I have no time which
do process work list.. TT

25. I will help you!

26. DMA controller
-In principle memory has only one handler that
can management and change his contents, It's a
CPU
-But the one memory hadler system had
some problems like previous case (occured so
many interrupt)
-DMA controller can be directly access in
memory and handle, So at least IO processing
he works with memory instead CPU.
-Now Cpu takes his time which can do another
process's work list

27. Mode bit and system call

28. CPU has two modes and flag bit that be distinguish two mode
Mode bit 1 Mode bit 0

29. CPU on state mode bit 0 can exacute any instruction,
It is right of Operating system
But with mode bit 1, cpu have limitation of exacutable
instructions.
The IO instructions are representative Operating systems
right!

30. Lets Reconsider that process request IO processing situation
The IO processing is totally Operating system's right,
So user process flow must be jumped into OS
But It's impossible because the mode bit was 1,
The solution is create and send interrupt that allow
cpu change mode bit.
We call this process(not a computer term) System Call,
that change mode bit with trap and let process flow
jump into OS
And then CPU can be able to request
or accept about IO processing