CS162, Spring 1998
Midterm #1
Professor Alan Smith
Problem #1
Explain the difference between a process and a thread. Define both. What are the tradeoffs between using one
and using the other? (14)
Problem #2
We discussed two mathematical quantities that are reasonable targets for optimization in scheduling:
minimizing ave(f(i)) and minimizing ave(f(i)/s(i)). Please explain what each is, and explain why we would
like to minimize it. (14)
Problem #3
Please provide code (of the same sort used in class) that will implement P & V using the "swap" operation
described in class. (18)
Problem #4
What is the difference between an interrupt and a trap? Define both. Please give at least two examples of
each. (12)
Problem #5
Why does rollback usually require checkpoints? Please define both terms and explain. (11)
Problem #6
For each of FIFO, SRPT, and RR (Q=.25), and for the following set of arrival and service times, please show
a time line for which process is executing, and compute the mean flow time. Show your computations. (We
might give partial credit, if you made a simple and obvious error; we're not going to try to decode your
calculations if they aren't obvious.) (15)
  arrival service
A 0 1.5
B .3 .8
C 1.1 1.1
Problem #7
For the following two cases, please either show a complete safe sequence or show that there isn't one. (16)
PROCESS has-X has-Y max needs-X max needs-Y
A 10 20 75 50
B 0 70 50 90
CS 162, Midterm #1, Spring 1998
CS162, Spring 1998 Midterm #1 Professor Alan Smith 1
