Input/Output Control System (IOCS) is any of several packages on early IBM entry-level and mainframe computers that provided low level access to records on peripheral equipment. IOCS provides functionality similar to 1960s packages from other vendors, e.g., File Control Processor (FCP) in RCA 3301 Realcom Operating System, GEFRC in GECOS, and to the later Record Management Services (RMS) in DEC VAX/VMS (later OpenVMS.) In some cases IOCS was designed to coexist with Simultaneous Peripheral Operations On-line (SPOOL) software.