süsteemikõned

Süsteemikõned, also known as system calls, are the fundamental interface between a user program and the operating system kernel. When a program needs to perform an operation that requires privileged access to hardware or system resources, such as reading from a file, creating a new process, or allocating memory, it cannot perform these actions directly. Instead, it must request the operating system to perform these actions on its behalf. This request is made through a system call.

System calls are typically invoked using special instructions that trigger a transition from user mode to kernel mode. The program provides parameters to the system call, indicating the specific operation it wants to perform and any necessary data. The operating system kernel then validates these parameters and executes the requested operation. Once the operation is complete, the kernel returns control to the user program, often with a result or an error code.

The set of available system calls varies depending on the operating system. Common system calls include those for process management (e.g., fork, exec, exit), file I/O (e.g., open, read, write, close), memory management (e.g., sbrk, mmap), and inter-process communication. Programmers often interact with system calls indirectly through libraries or API functions that abstract away the low-level details of the system call interface. Understanding system calls is crucial for comprehending how programs interact with the operating system and for developing efficient and secure software.