System Call – It is the interface between the userspace program and kernel program to requests for resources.

Now why we need system calls-

• Reading and writing from files demand system calls.
• If a file system wants to create or delete files, system calls are required.
• System calls are used for the creation and management of new processes.
• Network connections need system calls for sending and receiving packets.
• Access to hardware devices like scanner, printer, need a system call.

Here are the five types of System Calls in OS:

• Process Control – This system call deals with process creation and termination, wait & signal events and allocate and free memory.
• File Management – This deals with the file manipulation like create, update, delete, read, write and add attributes to the file.
• Device Management – This deals with the device buffers like reading and writing as well as adding and removing logical devices.
• Information Maintenance – It handle the data transfer between user and OS kernel.
• Communications – This is used for inter process communication. Create and delete communication connections, send and receive messages etc.