notes on operating systems

1. OPERATING SYSTEMS STRUCTURES
 Several structures can be used to implement the
operating system. Operating systems are designed
using various structural methods to efficiently manage
system resources and provide services to applications.
 The design of a new operating system is a major task.
It is important that the goals of the system be well
defined before the design begins.
 The structure of the OS depends mainly on how the
various standard components of the operating system
are interconnected and melded into the kernel.

2. KERNEL
Kernel is central component of an
operating system that manages
operations of computer and
hardware.
Kernel acts as a bridge between
applications and data processing
performed.
This kernel is the code that manages
EVERYTHING on your computer, by
using the CPU.
Is Kernel a software or hardware?
Is Kernel CPU?
Which of them is the brain of a computer?

3. 1.Simple/Monolithic Structure
2.Micro-Kernel Structure
3.Hybrid-Kernel Structure
4.Exo-Kernel Structure
5.Layered Structure
6.Modular Structure
We have the following structures
in the operating system:

4. Simple/Monolithic structure
Such operating systems do not have well-defined structures
and are small, simple, and limited.
MS-DOS is an example of such an operating system
Entire operating system resides in kernel space
The kernel are easy to develop
All kernel functions are tightly integrated
High performance
Less Modularity
All components and modules
are bundled together.

5. Micro-kernel Structure
This structure designs the operating system by
removing all non-essential components from the
kernel and implementing them as system and
user programs. This results in a smaller kernel
called the micro-kernel.
Designed to provide only the most basic services:
memory management and process scheduling
 Other services, such as device drivers and file
systems, are implemented as user-level processes
This design allows the operating system to be more
modular and flexible
provides a more secure and stable operating system

6. STRUCTURE OF MONOLITHIC AND MICROKERNEL-
BASED OPERATING SYSTEMS, RESPECTIVELY

7. Hybrid-Kernel Structure
Hybrid-kernel structure is nothing but just a combination
of both monolithic-kernel structure and micro-kernel
structure.
 Good performance
 It supports a wide range of hardware and applications
 It increases overall complexity of system, and making
the system difficult to understand
 Increases time complexity

8. STRUCTURE OF MONOLITHIC KERNEL, MICROKERNEL
AND HYBRID KERNEL-BASED OPERATING SYSTEMS

9. EXO-KERNEL STRUCTURE
The exokernel architecture represents a
departure from traditional monolithic
and microkernel designs, emphasizing
resource exposition, customization, and
performance optimization. By exposing
hardware resources directly to
applications and providing fine-grained
control over resource management,
exokernels offer a flexible and efficient
platform for developing specialized
applications with specific performance
and security requirements.

10. Layered structure
An OS can be broken into pieces and retain much more
control over the system. In this structure, the OS is
broken into a number of layers (levels). The bottom layer
(layer 0) is the hardware, and the topmost layer (layer N)
is the user interface.

11. Modular Structure
It is regarded as the OS's ideal
strategy. It entails creating a
modular kernel design. Other
services are introduced to the
kernel as dynamically
loadable modules either
during runtime or startup
time. The kernel consists of
only a few fundamental
components.

12. Class questions
1. What is the main function of an operating system?
A) Managing computer hardware and software resources
B) Executing user programs
C) Providing a user-friendly interface
D) Monitoring network traffic
2. Which component of the operating system is
responsible for managing processes?
A) Kernel
B) Device drivers
C) System utilities
D) User interface
3. What is the purpose of a device driver in an
operating system?
A) Managing processes
B) Handling user input
C) Controlling peripheral devices
D) Providing graphical user interface
4. Which of the following is NOT a function of the
operating system?
A) Allocating memory to processes
B) Translating high-level programming languages to
machine code
C) Managing file systems
D) Providing entertainment applications
5. Which type of operating system structure
provides a high level of flexibility and modularity?
A) Monolithic kernel
B) Microkernel
C) Exokernel
D) Layered approach
6. What does the term "process" refer to in the
context of operating systems?
A) A running program
B) A type of file system
C) A device driver
D) A type of user interface