study 4 - 4th set of questions

------------------------------------------------------------------------

1. describe the difference between a function call and a system call.

2. what is an "exception"

3. explain what happens when a program
                    divides by zero
                    tries to write to a null pointer
                    tries to write to a valid virtual address where there
happens to
                           to be no physical memory

4. why does a read system call possiby cause the operating system to suspend
the
                     executing process and allow another process to run

5. how do you deal with the possible wrap around of the microseconds field
in gettimeofday?

6. if you are trying to find out how fast a program (function) runs what is
good about the rtdsc cycle counter mechanism?

7. what can be misleading about the cycle counter mechanism?  can it ever be
faster than reality?

8. if you wanted to measure the speed of a single add instruction and you
know it only takes a few cycles,
what is one approach to trying to measure that speed in reality ?

9.  how might the CPU cache memory system disrupt a measurement?

10. would gettimeofday() be useful for measuring 1 nanosecond of elapsed
time?