What do all three kernels have in common

What do all three kernels have in common?

its good we know what Kernel is first.  

Kernel is central component of an operating system that manages operations of computer and hardware. It basically manages operations of memory and CPU time. It is core component of an operating system. Kernel acts as a bridge between applications and data processing performed at hardware level using inter-process communication and system calls. Kernel loads first into memory when an operating system is loaded and remains into memory until operating system is shut down again. 

kernel is the main component of any operating system. The function or role of a kernel includes memory management, device management, and accessing all computer resources. Based on the functions, there are three main categories of OS kernel. Below shows the three main categories of Kernel. 

Now that we have discussed what Kernel is all about and the three main categories of Kernel, let us now examine what they all have in common. 



1. They all have kernel mode.

2.  They all interact with hardware and applications.

3. They all have virtual memory.

4. They all have Inter-process communications (IPC).



Monolithic kernel

The operating system code is in a single executable image in a monolithic kernel. In this architecture, the entire operating system is working in kernel space. In other words, no parts of the OS are in user mode (low privilege). The monolithic kernel alone defines a high-level virtual interface over computer hardware to provide its services. Look at the figures below to understand the function of the monolithic kernel.

Note:  All the services run in kernel space.

Examples of operating systems with Monolithic kernels include the Linux kernel and the original Unix kernels
Advantages of Monolithic Kernel

• Simplicity: Monolithic kernels are simpler to design and implement compared to microkernels.
• Performance: Because all the components are part of the same module, communication between them is fast and efficient, leading to better performance.
• Flexibility: Monolithic kernels can be easily modified and extended, making it easier to add new features and improve existing ones.

Disadvantages of Monolithic Kernel

• Scalability: As the operating system grows, the size of the monolithic kernel also grows, making it more difficult to maintain and debug.
• Stability: A bug in any part of the monolithic kernel can potentially crash the entire system, making it less stable.
• Security: Because all components are part of the same module, a security breach in one part of the system can potentially compromise the entire system.

Micro Kernel

A microkernel is a software or a program that contains both user and kernel services in separate address spaces. Due to which the size of the Microkernel is smaller than that of the Monolithic kernel. As the user services and the kernel services reside in different address spaces, for communication purposes, message passing is used, which makes the execution of the microkernel to be slower. 

Note: The Microkernel is entirely responsible for the operating system's most important services like inter-process communication, memory management and CPU scheduling.

Examples of operating systems with Microkernels include QNX and the MINIX operating system.

Advantages of Micro Kernel

• Scalability: Because the microkernel is smaller and only includes the essential components, it is easier to maintain and extend, leading to better scalability.
• Stability: If a component crashes, only that component is affected and the rest of the system remains operational, making it more stable.
• Security: Because components run in separate user-mode processes, a security breach in one component cannot affect the entire system, leading to better security.

Disadvantages of Micro Kernel

• Performance: Communication between components is slower, as they are separated by the kernel and must go through system calls, leading to reduced performance.
• Complexity: Microkernels are more complex to design and implement compared to monolithic kernels.
• Integration: Integrating components can be more difficult, as they are separate from the kernel and must be carefully managed.

Hybrid Kernel

A Hybrid kernel is a combination of both Monolithic and Microkernel architecture. It combines the advantages of both and tries to overcome the disadvantages of each. A Hybrid kernel has a larger kernel than a microkernel but smaller than a monolithic kernel.

Examples of operating systems with Hybrid Kernels include Microsoft Windows NT and Apple’s macOS.

Advantages of Hybrid Kernel

• Performance: A Hybrid kernel combines the fast communication between components of a Monolithic kernel with the stability and security benefits of a Microkernel.
• Scalability: The smaller size of the kernel compared to a Monolithic kernel makes it easier to maintain and extend, leading to better scalability.
• Flexibility: The larger kernel compared to a Microkernel allows for more components to be included and integrated, leading to better flexibility.

Disadvantages of Hybrid Kernel

• Complexity: Hybrid kernels are more complex than both Monolithic and Microkernels, as they must balance the advantages and disadvantages of both.
• Integration: Integrating components can be difficult, as they must be carefully managed and balanced with the size and functionality of the kernel.
• Performance trade-off: While a Hybrid kernel can improve performance compared to a Microkernel, it may still be slower than a Monolithic kernel due to the separation of components.