1.2 The Role of the Operating System

Question 1

Kernel

Answer 1

• Most essential part of OS
• Runs in Privileged mode, having exclusive access to Hardware
• Error Handling, if application wants to acces hardware or privileged instuctions

Question 2

System Call

Answer 2

Interfaces between application program, operating system, and hardware

For software, they are often standardized and encapsulated in system libraries

For hardware, special machine instructions of the respective processor family are used when transitioning from user mode to kernel mode.

Question 3

How do system calls work?

Answer 3

1. Application performs system call to acces Hardware
2. OS provides Interface/functioncalls via specialized Library
3. OS switches to kernel Mode
4. OS Performs function on behalf of Hardware
5. OS returns to user mode
6. Resumes communication with software

Question 4

Interrupt Controller

Answer 4

• Part of the CPU
• Handles incoming interruption signals
• Interrupts current execution and triggers jump into OS

Question 5

How does Interruption Handling works?

Answer 5

1. Error/Interruption signal comes in
2. Interruption controler changes programm counter to fix interruption
3. OS switches in privileged mode
4. Old value of counter still stored
5. Resumed after interruption is handled

Question 6

Functions of the OS

Answer 6

Manages and controls application execution
and Interaction between software and Hardware

Providing User Interfaces
* GUI
* CLI

User, Device, Resource Management
* Access rights
* Drivers - allow OS to communicate to hardware

System Security and Monitoring

Question 7

What is a Device Driver

Answer 7

• A device driver is a set of program code that controls communication between the machine and an attached device.
• In an operating system, it enables this code to interact directly with the hardware by executing it in the privileged kernel mode.
• The device drivers are loaded into the kernel as software modules for this purpose.