Comp111 - Quiz 2 Review 4 Answers

Dec 8, 2009 - closed book

Name:____Answers_____________________

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Please fill in the blanks. Each blank is worth 5 points. Blanks with the same number have the same answer.

  1. The exponential distribution is ____memoryless____ , i.e., the time taken by one request is ____independent/uncoupled____ from the times for previous requests.
  2. In segmented memory addressing, a memory address is treated as containing three sub-addresses describing the ____segment [offset]____, ____page [offset]_____ and ____byte [offset]____ of the memory location. Segments are utilized in order to group pages that should share the same ____protections/state____; this saves ____memory____ that would otherwise be needed to store this information for each page or word.
  3. When one opens a file, the ____process____ gets a descriptor that points to a ____kernel object/descriptor____ that is shared by any processes that happen to open the file.
  4. Every UNIX file has a corresponding ____inode____ that contains information on the file's location, ____owner or type____, group, and protections.
  5. If the power fails unexpectedly on a filesystem, then a specific block might be simultaneously inside a file and on the ____free____ list. This is because blocks are written to the physical disk as ____late____ as possible.
  6. Writing a byte to disk is a complicated procedure. First the ____sector/block____ containing the byte is read into memory, modified, and marked as ____dirty/modified____. At some later time, all ____dirty/modified____ pages are flushed to disk. In a journalling filesystem, these are stored as ____transactions/change requests/etc____ in a special part of the disk.
  7. A device ____driver____ is a program that controls a physical or pseudo device. The ____major____ number of a device identifies the driver, while the ____minor____ number identifies the specific device or options.
  8. One of the things that makes I/O subsystems difficult to understand is that they are composed from producer-consumer relationships at different scales. The ____device____ requires information in a specific format and in chunks it can manage, while the application provides that information in different-size chunks.