General

Question 1

What are the roles of the OS?

Answer 1

• Provide an environment in which we can run programs
  *I/O operations, file system access, accounting, shared
  libraries, communication between processes
• Allocate and manage scarce resources
• Memory, CPU, network activity
• Control processes
• Process creation, execution, protection, error/conflict
  detection and response, security

Question 2

How does the OS remain in control?

Answer 2

Interrupts that return control of the CPU to the OS.

Question 3

Synchronous VS. Asynchronous

Answer 3

Synchronous:
Executing program needs to be aware of event as it happens
Asynchronous:
The event happens independently of the executing program and the program can deal with it later

Question 4

Event detection by:

• Polling
• Interrupts

Answer 4

Polling:
- The program continually asks the device/system about whether or not a particular event has happened
-Integrated into the normal flow of the program
Interrupts:
-The entity that is causing the event notifies the program (via the OS) when the event happens.
-Program flow is diverted to deal with the event as it happens.
modeled as an exception to the normal flow of the program.