COEN 180
Midterm 2 Sample Questions
  1. Explain Hamming distance, using as an example the words 01010101 and 11111111.
  2. Explain: If two code words have a Hamming distance of two, then the code cannot correct always a single error.
  3. Give the parity matrix of a systematic Hamming code with 3 parity symbols and 4 information symbols. Encode message 1100 with this code. Then change the third bit from the left in the encoding and show how the receiver corrects this transmission mistake. Now change the third and the fourth bit and calculate the correction that the code makes.
  4. Draw a cross section through a CD-ROM and explain in detail how the optical data is encoded and decoded.
  5. Explain why CD-ROM do not use a simple encoding where a 1 corresponds to a pit and a 0 corresponds to a land area.
  6. Draw a cross section to a two layer DVD and explain how data from both layers are being read.
  7. Explain why CD (and DVD) players have a noticeable seek time (moving to a random location) compared to magnetic disks.
  8. Why is the data density of optical recording limited?
  9. Define by diagram and word for magnetic recording on hard drives: "Sector", "Track", "Cylinder", "Latency", "Band".
  10. Explain the write and read procedure of an inductive head. Show the write and read currents in the inductive head.
  11. What is the (giant) magneto-resistive effect and how is it being used in magnetic read heads?
  12. Explain the phases of a random disk access.
  13. Why are accesses to an object stored in contiguous sectors of a disk faster than access to the same object stored in random sectors. (I.e., why does disk defragmentation help disk performance)
  14. What is the latency of a disk rotating at 12,000 rotations per minute?
  15. Give and define the error sources in disk drive operations.
  16. Explain why lowering the head - surface distance is important for increasing data density.
  17. Explain how higher rotational speed, platter diameter, and access times are related.
In addition, all homework questions are templates of midterm questions.
© 2003 Thomas Schwarz, S.J., COEN, SCU                                                                              SCU            COEN            T. Schwarz            COEN 180