Computer Organization I, HT 4

1. [2 htp] Hamming code.
   1. Show how error correcting Hamming code recognizes and corrects a mistake when in a 7-bit data "011 0100" the 3. bit from left has changed erroneously into zero: "010 0100".
      These 7 bits contain both the data and parity bits.
   2. How many wires (bits) does one need to protect a 32-bit data bus with error correcting Hamming code?
      (We want to move 32 bits of data in addition to the parity bits)
   3. Why is Hamming code not a good approach to secure LAN data transfers?
      
      
2. [2 htp] Assume that there is an operating system for TTK-91. One part of that OS is the process control.  Assume further that due to a clock interrupt we need to switch the process that runs on the processor.
   1. How and where are the data for the process earlier in execution stored? Which data must be stored?
   2. How and from where does one find the data for the new process? Where is the first instruction for the new process? How is the processor turn actually given to the new process?
   3. What is the processor state (user, priviledged) from the time just before the clock interrupt until the execution of the first instruction of the new process?

3. [2 htp] Proces states. In Lesson 8 [Stal06, Ch 8.2] we introduced the process life time model, which included five model states. Give two clearly different examples to each situation given below. Mention also, who (which process) caused the state transition and what happens in the operating system data structures during the transition.
   1. Process P moves from "New" state to "Blocked" state.
   2. Prosess P moves from "Running" state to "Blocked" state.
   3. Prosess P moves from "Ready" state to "Running" state.
   4. Prosess P moves from "Running" state to "Ready" state.
   5. Prosess P moves to "Exit" state.
       
4. [1 htp] Prosess. Could one implement an operating system without processes?
   If one could, what would it mean? If one can not, why?