System Call:

System calls provide an interface between the processor and the operating system. System calls allow user-level processes to request some services from the operating system which process itself is not allowed to do. For example, for I/O a process involves a system call telling the operating system to read or write a particular area and this request is satisfied by the operating system.

The following different types of system calls provided by an operating system:-

Process control

• end, abort
• load, execute
• create a process, terminate the process
• get process attributes, set process attributes
• wait for time
• wait for the event, a signal event
• allocate and free memory

File management

• create a file, delete a file
• open, close
• read, write, reposition
• get file attributes, set file attributes

Device management

• request device, the release device
• read, write, reposition
• get device attributes, set device attributes
• logically attach or detach devices

Information maintenance

• get time or date, set time or date
• get system data, set system data
• get process, file, or device attributes
• a set process, file, or device attributes

Communications

• create, delete communication connection
• send, receive messages
• transfer status information
• attach or detach remote devices