System calls

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Resource Management[1]
System calls happen between the application and operating system layer part of this diagram.
This diagram shows a simplified representation of a system call[2].


In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the kernel of the operating system on which it is executed. This may include hardware-related services (for example, accessing a hard disk drive), creation and execution of new processes, and communication with integral kernel services such as process scheduling. System calls provide an essential interface between a process and the operating system.[3]

Categories of system calls can be grouped as noted below[4]:

  1. Process control
    • create process (for example, fork (operating system)|fork on Unix-like systems, or NtCreateProcess in the Windows NT, Native API)
    • Kill (command)|terminate process
    • Loader (computing)|load, Exec (operating system)|execute
    • get/set process attributes
    • Wait (operating system)|wait for time, wait event, Signal (computing)|signal event
    • Dynamic memory allocation|allocate and Garbage collection (computer science)|free memory
  2. File management
    • create file, delete file
    • open, close
    • read, write, reposition
    • get/set file attributes
  3. Device management
    • request device, release device
    • read, write, reposition
    • get/set device attributes
    • logically attach or detach devices
  4. Information maintenance
    • get/set time or date
    • get/set system data
    • get/set process, file, or device attributes
  5. Communication
    • create, delete communication connection
    • send, receive messages
    • transfer status information
    • attach or detach remote devices
  6. Protection
    • get/set file permissions

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References