KernelModeUserMode

KernelModeUserMode refers to the two distinct privilege levels at which software can execute on an operating system. User mode is the less privileged level, where most applications and programs run. These applications have limited access to the system's hardware and memory, and they must make requests to the operating system's kernel to perform privileged operations. This isolation is a security feature, preventing errant or malicious applications from corrupting the entire system.

Kernel mode, also known as supervisor mode or ring 0, is the highly privileged level. The operating system's kernel, device drivers, and other core system components execute in kernel mode. This mode grants direct access to all system memory and hardware, allowing the kernel to manage resources, schedule processes, and enforce security policies. When a user-mode application needs to perform a task that requires kernel privileges, it triggers a system call, which transitions the processor from user mode to kernel mode. The kernel then performs the requested operation on behalf of the application and returns control back to user mode. This context switching mechanism is fundamental to the operation of modern operating systems, ensuring both stability and security.