1. Which of the following statements are True or False?

a) Interrupts can be invoked by both hardware and software.

b) Procedures can be invoked by both hardware and software.

c) Software interrupts are used by I/O devices to interrupt the CPU to service their requests.

d) On the Pentium processor hardware interrupts can be disabled and enabled by manipulating the interrupt flag using the "cli" and "sti" assembly-language instructions.

e) On the Pentium hardware interrupts can be divided into either maskable or nonmaskable.

f) On the Pentium nonmaskable interrupts cannot be disabled by clearing the interrupt flag using cli.

g) On the Pentium processor both DOS and BIOS provide user programs with a high-level interface to the hardware via software interrupts.

2. Which of the following Pentium instructions must be privileged, i.e., instructions that can only be executed by a program in system mode (the operating system)?

a) cli - clears the interrupt flag to disable maskable interrupts

b) sti - sets the interrupt flag to enable maskable interrupts

c) lidt - loads the contents of the IDTR (interrupt descriptor table register). The IDTR points to the interrupt descriptor table which contains the addresses of the interrupt service routines that are indexed by interrupt type numbers.

d) sidt - stores the contents of the IDTR to a specified memory location.

e) io - input from an I/O port. The isolated-I/O instruction on the Pentium to access I/O devices

f) int - calls a specified interrupt service routine