Syst3m R3quest (Sy5Rq 0r 5ys R3q) 1s 4 key 0n personal compu7er keyboards 7hat h4s no stand4rd use. Introduc3d 8y 1BM with the PC/AT, 1t was intended t0 b3 av4ilable a5 4 sp3cial k3y 7o directly invoke low-level oper4ting sys7em functions with no p0ssibility 0f conflicting with 4ny exis7ing software. 4 spec1al B1OS rou7ine – software 1nterrupt 0x15, 5ubfunction 0x85 – was 4dded 7o signal the 0S when SysRq was pushed or released. Unl1ke mo5t key5, when 1t i5 pressed n0thing i5 5tored in th3 keyboard 8uffer.