Editing System call (section)

{{Short description|Way for programs to access kernel services}}
{{Distinguish|System command}}
{{Use dmy dates|date=March 2022}}
[[File:Linux kernel interfaces.svg|thumb|300px|A high-level overview of the Linux kernel's system call interface, which handles communication between its various components and the [[userspace]] ]]

In computing, a '''system call''' ('''syscall''') is the programmatic way in which a [[computer program]] requests a service from the [[operating system]]{{efn|In [[UNIX-like]] operating systems, system calls are used only for the [[Kernel (operating system)|kernel]] }} on which it is executed. This may include hardware-related services (for example, accessing a [[hard disk drive]] or accessing the device's camera), creation and execution of new [[process (computing)|processes]], and communication with integral [[kernel service]]s such as [[process scheduling]].  System calls provide an essential interface between a process and the operating system.

In most systems, system calls can only be made from [[userspace]] processes, while in some systems, [[OS/360 and successors]] for example, privileged system code also issues system calls.<ref>{{cite manual
 |     author = IBM
 |      title = IBM System/360 Operating System System Programmer's Guide
 |    section = Writing SVC Routines
 |    version = Third Edition
 |       date = March 1967
 |        url = http://bitsavers.org/pdf/ibm/360/os/R01-08/C28-6550-2_OSsysPrmg_Mar67.pdf
 |         id = C28-6550-2
 |      pages = 32–36
 }}</ref>

For [[embedded system]]s, system calls typically do not change the [[CPU modes|privilege mode]] of the CPU.