Introduction of System Call:
A system call is an essential mechanism that enables user-level processes to interact with the operating system kernel. It provides a bridge between the user-level application and the underlying hardware resources of the system.
When a process needs to perform some privileged operation, such as reading from a file, writing to a network socket, or allocating memory, it cannot directly access the hardware resources. Instead, it must request the operating system to perform the operation on its behalf by making a system call.
The system call interface provides a set of standard functions that a process can use to request services from the kernel. The operating system maintains a table of system calls, each identified by a unique number, called a system call number or syscall.
When a process wants to make a system call, it provides the syscall number and any required arguments to the kernel by issuing a software interrupt or trap. The kernel then checks the validity of the arguments and executes the requested operation on behalf of the process. Once the operation is completed, the kernel returns the result to the calling process.
System calls are essential for the proper functioning of the operating system(os). They provide a standardized way for processes to access kernel services, which makes it easier for developers to write applications that can run on different operating systems.
Some of the commonly used system calls in operating systems include:
- read(): Reads data from a file or other input stream.
- write(): Writes data to a file or other output stream.
- open(): Opens a file for reading or writing.
- close(): Closes a file or other resource.
- fork(): Creates a new process by duplicating the calling process.
- exec(): Replaces the current process with a new process.
- wait(): Waits for a child process to terminate.
- exit(): Terminates the calling process.
Understanding system calls is essential for developers who want to write efficient and reliable applications. It is also important for system administrators who need to understand the underlying mechanisms of the operating system to troubleshoot performance or reliability issues.