Editing System request (section)

{{Short description|Computer key}}
{{Redirect|SysReq|prerequisites for computer software|System requirements}}
[[Image:KeyboardWithPrintScreenRinged.svg|thumb|A 104-key [[Personal computer|PC]] [[United States|US]] [[English language|English]] [[keyboard layout]] with System request circled|400x400px]]
'''System Request''' ('''SysRq''' or '''Sys Req''') is a key on [[IBM PC compatible|personal computer]] [[Computer keyboard|keyboards]] that has no standard use. Introduced by [[IBM]] with the [[IBM Personal Computer/AT|PC/AT]], it was intended to be available as a special key to directly invoke low-level [[operating system]] functions with no possibility of conflicting with any existing software. A special [[BIOS]] routine – software interrupt 0x15, subfunction 0x85<ref name="intlist">{{cite web|title=Ralf Brown's Interrupt List|url=http://www.delorie.com/djgpp/doc/rbinter/id/30/15.html|access-date=2018-06-21}}</ref> – was added to signal the [[operating system|OS]] when SysRq was pushed or released. Unlike most keys, when it is pressed nothing is stored in the [[keyboard buffer]].