käyttäjätilat

Käyttäjätilat are a concept in operating systems that refers to the execution environment where user applications run. This environment is distinct from the kernel mode, where the operating system's core functions and privileged operations are handled. The primary purpose of separating user mode from kernel mode is to enhance system stability and security.

In user mode, applications have restricted access to hardware and system resources. They cannot directly interact with devices or modify critical system data. Instead, they must make requests to the operating system kernel through a mechanism called system calls. When an application needs to perform a privileged operation, such as reading a file or allocating memory, it triggers a system call. The operating system then transitions to kernel mode, performs the requested operation on behalf of the application, and returns the result to the application in user mode.

This separation prevents errant or malicious user applications from corrupting the operating system or interfering with other processes. If an application crashes or behaves unexpectedly in user mode, it typically only affects that specific application, not the entire system. The kernel mode, on the other hand, is protected and can only be accessed through controlled interfaces. This design principle is fundamental to modern operating system architectures, ensuring a robust and secure computing environment.