CS360 Final -- December 10, 2002

Answers to Question 5

• A. Malloc() buffers the sbrk() system call. True. See the Malloc lecture notes.

• B. Zombie processes waste a significant amount of memory. False. They are just placeholder processes -- yes, they waste a process id and enough information to return to wait(), but that is just a few bytes. If you don't believe me, see this quote from the exec/wait lecture notes:
  By a "zombie", we mean that it takes up no resources, and doesn't run, but it is just being maintained by the operating system so that when the parent calls wait(), it will get the proper information.

• C. My program will typically generate a segmentation violation if I try to overwrite the instructions in memory. True. See the memory lecture notes.

• D. Processes communicate through shared memory with the fork() system call. False. They can only communicate through the operating system.

• E. You can avoid catching the SIGPIPE signal if you use threads. False. If your process tries to write to a pipe (or socket) with no read end, it will generate SIGPIPE, and if you don't catch it, your process will die. Even if you use threads.

• F. My program will typically generate a segmentation violation if I try to write into memory that is above (less than) the current value of the stack pointer. False. You get stack space by decrementing the stack pointer -- the memory is already there. See the Malloc lecture notes.

• G. Pipe() allows processes to communicate through a buffer in the operating system. True. See the pipe lecture notes.

• H. Telnet allows me to write a server program that others on the Internet may use effectively even if all they know is my server's host name and port number. True. Telnet is a generalized client program that serves that exact function.

Grading: 8 points