Name:_____________________

UTD ID#:_________________

Notes: 1. Answer all 6 questions within the space provided.2. Anything written outside the provided space will be ignored. 3. Use the back side as scratch pad.

4. Write your name and UTD_ID on all sheets you use.

1. Memory access time is 10 nanoseconds, instruction decode/execution time is 5 nanoseconds. 50% of the instructions executed require no operands from memory and the rest of the executed instructions require one operand from the memory. What is the number of instructions executed in one second? Show the steps in arriving at your answer.

2. What is the need for two modes of operations: user mode and system/kernal/monitor mode?

3. In multiprogrammed OS, how do you ensure that one program does not access memory which belongs to another program?

4. Describe the important steps involved in migrating a process from computer system A to computer system B. State important assumptions you make.

5. Write a multi-threaded program that creates 20 threads. Thread i (i=1, 2, …, 20) must print the numbers i*100, i*100+1, …, i*100+50.

6. There is a parking lot P that has space for 250 vehicles with one entry gate and one exit gate, both of which are operated automatically. If the lot is full, all vehicles wishing to enter are to be stopped at the entrance. Every time a vehicle arrives at the entry gate, an appropriately placed sensor performs a signal operation on semaphore sem_entry. (The sensors do not do anything if the vehicle is stationary near the entrance.) Similarly, when a vehicle arrives at the exit gate, an appropriately placed sensor performs a signal operation on semaphore sem_exit. Two appropriately names functions raise_entry_gate() and raise_exit_gate() are available. (As soon as one vehicle enters/exits, the entry/exit gate automatically lowers.)

Develop a solution using semaphores to operate the two gates. Specify initial values for all semaphores used. Give brief explanation of the important steps of your program.