System Call:
In computing, a system call is the programmatic way in which a computer program requests a service from the kernel of the operating system it is executed on. A system call is a way for programs to interact with the operating system.
System calls
provide an interface between the process and the operating system.
System calls
allow user-level processes to request some services from the operating system which itself is not allowed to do.
System call provides the services of the operating system to the user programs via Application Program Interface(API).
System calls are the only entry points into the kernel system. All programs needing resources must use system calls.
For example, for I/O a process
involves a system call telling the operating system to read or write 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 process, terminate
process
• get process attributes, set
process attributes
• wait for time
• wait event, signal event
• allocate and free memory
File management
• create file, delete file
• open, close
• read, write, reposition
• get file attributes, set file
attributes
Device
management
• request device, 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
• set process, file, or device
attributes
Communications
• create, delete communication
connection
• send, receive messages
• transfer status information
• attach or detach remote devices
Protection
. set permissions
and get permissions
. allow user and
deny user.
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