What are system calls?

System calls are a crucial interface in the operating system (OS) that provides an interface between a process and the operating system. These calls are how a program requests a service from the OS’s kernel, which is the core component managing system resources. System calls are necessary for performing various operations such as file manipulation (opening, reading, writing, and closing files), process control (creation, execution, termination), and communication (sending and receiving messages, establishing or releasing connections). They are implemented via software interrupt instructions, which switch the processor from user mode to kernel mode, where the operating system has control and can safely perform hardware operations or sensitive tasks. This mechanism ensures system stability and security by abstracting hardware details and providing a controlled way to access resources.