CSE 120 -- Homework #1

1. Chapter 1: 1, 4, 7, 8, 13, 14

2. [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?

3. [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.

4. [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 your answer.