[[!meta copyright="Copyright © 2010 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU Free Documentation License|/fdl]]."]]"""]] In an [[UNIX]]-like system, a *system call* (*syscall*) is used to request all kinds of functionality from the operating system kernel. A [[microkernel]]-based system typically won't offer a lot of system calls -- apart from one central one, and that is *send message* -- but instead [[RPC]]s will be used instead. In the [[GNU Hurd|hurd]], a lot of what is traditionlly considered to be a UNIX system call is implemented (primarily by means of [[RPC]]) inside [[glibc]].