CSE 120 -- Homework #1
- Chapter 1: 1, 4, 7, 8, 13, 14
- [Crowley] Suppose the hardware interval timer only counts
down to zero before signalling an interupt. How could an OS
use the interval timer to keep track of the time of day?
- [Silberschatz] Protecting the operating system is crucial to
ensuring that the computer system operates correctly. Provision of
this protection is the reason behind user/kernel operation, memory
protection, and the timer. To allow maximum flexibility, however, we
would also like to place minimal constraints on the user. The
following is a list of operations that are normally protected. What
is the minimal set of instructions that must be protected?
- Change to user mode.
- Change to kernel mode.
- Read from kernel memory.
- Write into kernel memory.
- Fetch an instruction from kernel memory.
- Turn on timer interrupt.
- Turn off timer interrupt.
- [Silberschatz] Consider what you have read and heard about the
definition of an operating system. Should an application like a Web
browser be considered part of an operating system? Briefly justify