Components of OS

Components of the Operating System:

1) User space: The user space in an operating system does not have direct access to hardware. For example, when you turn on a Windows laptop, the desktop with icons that you see is part of the user space, also known as the Graphical User Interface (GUI). In Linux or Ubuntu, you can use a terminal, which is known as the Command Line Interface (CLI). In the CLI, you write commands to perform tasks such as opening folders, similar to how you would use the GUI in Windows by just simply clicking the folder. It interacts with the kernel to access hardware.

2) Kernel: It is also known as the heart of OS. It directly interacts with the hardware. Its the very first part of OS to load and start. The switching between user space and kernel is done through software interrupt. For example, when you issue a command such as 'mkdir' to create a new folder, you are operating in user mode. Upon pressing Enter, a system call i.e. software interrupt is invoked, which causes a transition from user mode to kernel mode. This switch allows the operating system to handle the file management operation. Once the folder creation is completed, the system returns to user mode.



Functions of kernel:



Types of kernel:

1. Monolithic kernel: All the functions of the kernel are contained within the kernel itself. Since these functions are integrated within the kernel, they can communicate easily and quickly. The kernel is very bulky due to the presence of all functions in it. Moreover, if a function within the kernel, such as one handling memory management, encounters a critical failure, it can potentially cause the entire kernel to crash. 
Examples: Unix, Linux, MS-DOS

2. Micro kernel: In this architecture, the file management and input/output modules operate in user space, while other components are handled within the kernel. This separation keeps the kernel less bulky, enhancing its reliability since the kernel can continue functioning even if one of the user-space modules crashes. However, this design can lead to performance drawbacks, such as increased context switching, which may reduce overall system efficiency.
Example: Symbian OS, L4 Linux 

3. Hybrid kernel: In this operating system, the file management module operates in user space, while the rest of the system components are managed within the kernel. This setup combines elements of both microkernel and monolithic kernel architectures.
Example: MacOS, Windows 7 and above














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