Consider a system that has a cache memory unit and a memory management unit (MMU). The address input to the cache memory is a physical address. The MMU has a translation lookaside buffer (TLB). Assume that when a page is evicted from the main memory, the corresponding blocks in the cache are marked as invalid.

For a given memory reference, which of the following sequences of events can NEVER happen?

Consider a hard disk with a rotational speed of 15000 rpm . The time to move the read/ write head from a track to its adjacent track is 1 millisecond. Initially, the head is on track 0 . The number of sectors per track is 400 . The sector size is 1024 bytes. It is necessary to transfer data from 10 randomly located sectors in each of the following tracks in the order: 5,12 and 7.

The total time for the data transfer (in milliseconds) from the hard disk is $\_\_\_\_$ . (rounded off to one decimal place)

Consider the following program snippet. Assume that the program compiles and runs successfully. Further, assume that the fork( ) system call is always successful in creating a process.

int main( ) {

int i;

for (i = 0; i < 3; i++){

    if (fork() == 0){

        continue;

    }

    break;

}

printf("Hello!");

return 0;

}

```

The total number of times that the printf statement gets executed is $\_\_\_\_$ . (answer in integer)

Consider a CPU that has to execute two types of processes. The first type, Actuators (A), requires a CPU burst of 6 seconds. The second type, Controllers (C), requires a CPU burst of 8 seconds. A new process of type A arrives at time $t=10,20,30,40$, and 50 (in seconds). Similarly, a new process of type C arrives at time $t=11,22,33$, 44, and 55 (in seconds). The CPU scheduling policy is First Come First Serve (FCFS). The first process of type A starts running at $t=10$ seconds. The average waiting time (in seconds) for the 10 processes is $\_\_\_\_$ . (rounded off to one decimal place)