- List two challenges an OS faces when passing parameters between
user and kernel mode. Describe how an OS can overcome them.
- Chapter 1
1.12 Some computer systems do not provide a privileged mode
of operation in hardware. Is it possible to construct a
secure operating system for these computers? Give arguments
both that it is and that it is not possible.
- [Silberschatz] What are the differences between a trap and an
interrupt? What is the use of each function?
- [Silberschatz] Which of the following instructions should be
a) Set value of timer
b) Read the clock
c) Clear memory
d) Turn off interrupts
e) Switch from user to monitor mode
- [Silberschatz] Protecting the operating system is crucial
to ensuring that the computer system operates correctly. Provision of
this protection is the reason for dual mode opeartion, memory
protection, and the timer. To allow maximum flexibility, however, you
should also place minimal constraints on the use.
The following is a list of instructions that are normally
protected. What is the minimal set of instructions from this list that must
a) Change to user mode
b) Change to monitor mode
c) Read from monitor memory
d) Write into monitor memory
e) Fetch an instruction from monitor memory
f) Turn on timer interrupt
g) Turn off timer interrupt
- Chapter 2
2.11 It is sometimes difficult to achieve a layered approach if
two components of the operating system are dependent on each other.
Identify a scenario in which it is unclear how to layer two system
components that require tight coupling of their functionalities.
- The Java runtime provides a set of standard system libraries for
use by programs. To what extent are these libraries similar to the
system calls of an operating system, and to what extent are they
- [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?
- [Tanenbaum] One reason GUIs were initially slow to be adopted was
the cost of the hardware needed to support them. How much video RAM,
in bytes, is needed to support a 25 line X 80 row character monochrome
text screen? How much for a 1024 X 768 24-bit color bitmap? What was
the cost of this RAM at 1980 prices ($5/KB)? How much is it now (say,