System Call

A system call is a programmatic way in which a computer program requests a service from the kernel of the operating system on which it is executed.

System Calls are,

• A way for programs to interact with the operating system.
• Provide the services of the operating system to the user programs.
• Only entry points into the kernel and are executed in kernel mode.

How do System Calls Work?

• A system call allows a program to request services from the operating system.
• It can be written in high-level languages (C, C++, Pascal) or in assembly.
• When a program makes a system call, it switches to kernel mode.
• The OS handles the request, performs the task (e.g., file access, process control), and returns the result.
• Without system calls, each program would need its own way to access hardware, making systems inconsistent and error-prone.

Types of System Calls

Services provided by an OS are typically related to any kind of operation that a user program can perform like creation, termination, forking, moving, communication, etc. Similar types of operations are grouped into one single system call category. System calls are classified into the following categories:

Read more about - Different Types of System Calls in OS

• File System: Used to create, open, read, write, and manage files and directories.
• Process Control: Used to create, execute, synchronize, and terminate processes.
• Memory Management: Used to allocate, deallocate, and manage memory for processes.
• Interprocess Communication (IPC): Used for data exchange and communication between different processes.
• Device Management: Used to request and release devices, and to perform read/write operations on them.