Stanford Operating Systems Quals

2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992

1997 Problem Set

The objective of the exam is to find out what you know about operating systems and to assess your ability to identify and develop solutions for problems that arise in operatings systems. Note that the questions may have many "right" answers so be sure to justify your answers. In particular, state any assumptions you make when answering the questions. Point form answers are acceptable. Problem 1 (24 Points) A major focus of operating system research over the last ten years has been on building extensible operating systems.

(a) Provide the justification/motivation for building extensible operating systems. (i.e., What are the problems being solved?)

(b) Describe the criteria you would use to determine if an operating system is indeed an extensible operating system. (i.e., How do you tell an extensible operating system from a non-extensible one?)
Problem 2 (24 Points) Operating system algorithms are frequently influenced by hardware technology. For example, since DRAM memory loses its contents when electrical power is lost, operating systems typically do not assume that memory contains valuable information after a power failure. Consider what would happen if some new non-volatile memory technology replaces DRAMs. In this new technology, a memory location holds its current value even when power is lost.

Since the contents of main memory represent a large and costly part of the state of a modern computer system, the non-volatile memory technology appears to hold promise for building systems that can recover from a power failure crash nearly instantly after the power is restored.

(a) Describe the challenges facing an operating system that wants to use the non-volatile memory to speed recover from power failure crashes. What are the difficult problems that need to be solved?

(b) Describe how you might use this new memory to speed recovery from power failure crashes.
Problem 3 (12 Points) A technique used in most operating systems developed since Multics is device independant input/output. Describe the advantages and disadvantages of this technique.

Maintained by Gurmeet Singh Manku