User mode vs Kernel Mode

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Windows operating system operates in two distinct modes: user mode and kernel mode. These modes represent different levels of privilege and determine the level of access and control that applications and system components have over the system resources. Here's an explanation of user mode and kernel mode in Windows internals:
User Mode:
User mode is the execution environment where user applications and processes run. Applications, such as word processors, web browsers, and media players, operate primarily in user mode. In this mode, applications have restricted access to system resources and rely on the services provided by the operating system to perform tasks.
Key characteristics of user mode include:
Limited Privilege: User mode applications run with limited privileges, meaning they have restricted access to system resources and protected areas of the operating system. This restriction enhances system security by preventing unauthorized access or modification of critical resources.
Virtual Memory Management: User mode applications utilize virtual memory, a memory management technique that provides each application with its own virtual address space. Virtual memory isolates applications from each other, ensuring that one application cannot directly interfere with the memory of another.
Exception Handling: User mode applications can encounter exceptions or errors during execution. These exceptions, such as access violations or divide-by-zero errors, can be caught and handled within user mode. If an exception is not handled, the application may terminate.
User-Mode Services: User mode applications rely on user-mode services provided by the operating system, such as the graphical user interface (GUI), file systems, networking, and device drivers. These services abstract the complexities of system operations and provide a consistent interface for application developers.
Kernel Mode:
Kernel mode is the privileged execution environment where the Windows kernel operates. The kernel is the core component of the operating system responsible for managing system resources, enforcing security, and providing services to user mode applications.
Key characteristics of kernel mode include:
Unrestricted Privilege: The kernel has elevated privileges and full access to system resources, enabling it to perform critical operations and manage the hardware. It can access protected areas of memory, control devices, and modify system configurations.
Direct Hardware Access: Kernel mode has direct access to the underlying hardware components, such as the CPU, memory, and I/O devices. It can control and manage these resources, providing a layer of abstraction to user mode applications.
System Services: The kernel mode provides system services and functions that user mode applications rely on. These services include memory management, process scheduling, device drivers, file systems, network protocols, and more. Kernel mode components ensure the proper functioning of the operating system and facilitate communication between user mode and hardware.
Interrupt Handling: When hardware interrupts occur, such as user input or device events, the kernel mode handles these interrupts, interrupting the execution of user mode applications. The kernel manages and prioritizes these interrupts, allowing the system to respond promptly to hardware events.
It's important to note that operating system components and device drivers primarily operate in kernel mode. User mode applications interact with these components indirectly by making system calls or using APIs provided by the kernel.
The separation of user mode and kernel mode ensures system stability, security, and resource protection. User mode provides a controlled execution environment for applications, while kernel mode has elevated privileges to manage system resources and provide essential services.