CS 110 Homework Assignment 1
Due: Friday, February 8, 2002, at 9PM

Turn in your assignments in the bin outside Geoff's office. Late homework will be penalized; see the late policy for more information. We also will not accept handwritten material or printouts in which long lines are wrapped in the middle of a word. We prefer that you use a text processor. You might try troff or latex/xfig.

Also remember to date and time stamp your homework.

1. 3 points:
   MOS 1.4, p. 67. On early computers, every byte of data read or written was directly handled by the CPU (i.e., there was no DMA). What implications does this organization have for multiprogramming?
2. 2 points:
   How does the distinction between kernel mode and user mode function as a rudimentary form of protection (security) system?
3. 2 points:
   MOS #1.8, p. 68,
   Which of the following instructions should be allowed only in kernel mode?
   1. Disable all interrupts.
   2. Read the time-of-day clock.
   3. Set the time-of-day clock.
   4. Change the memory map.
4. 2 points:
   MOS #1.10, p. 69.
   A computer has a pipeline with four stages. Each stage takes the same time to do its work, namely, 1nsec. How many instructions per second can this machine execute?
5. 2 points:
   MOS 1.14, p. 68. What is the key difference between a trap and an interrupt?
6. 2 points:
   MOS #1.16, p. 70. Why is the process table needed in a timesharing system? Is it also needed in personal computer systems in which only one process exists, that process taking over the entire machine until it is finished?
7. 2 points:
   MOS #1.19, p. 70. Can the

   count = write(fg, buffer, nbytes);
   	

   call return any value in count other than nbytes? If so, why?
8. 2 points:
   Explain the difference between busy waiting and blocking.