study 5 - study questions

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1. what's wrong with this code:

if (fork() == 0) {
     execvp(argv[0], argv);
|/
/wait(&s);

2. explain fork, execl, execvp, wait,  and exit

3. a program may "commit suicide" or "be murdered",  give
one concrete example of how this might occur; e.g., we might
use the kill(1) command on a process as an example of being
murdered (send it a signal by hand).

4. what's wrong with the following i/o code

while((read(fd, buf, count) != 0)
       write(fd2, buf, count);
}

5. assume a shell starts 500 processes and each process randomly waits
from 1 to 10000 seconds before exiting.  Why is the simple wait(&status)
system call not up to dealing with this?

6. explain the following kinds of exceptions (what do they mean)

       hard disk interrupt

       clock interrupt

       segmentation violation exception

       page fault

       divide by zero

       software interrupt (a trap)

7. what is meant by context switch?  how is virtual memory affected?

8. what is meant by mode switch?  give an example of how a program might
experience a mode switch?

9. when a process forks,  what is shared with the child?  (what about open
file descriptors?)

10. in class, the instructor explained the difference between processes
and threads - explain in terms of

the text (machine code)
data (initialized or not initialized)
stack

which are shared in processes and which are shared in threads

11. give a rough explanation of what happens when a hard disk interrupt
occurs and a process is actually RUNNING in user space

12 explain what happens when a system call is executed by a program
running in user space?