The most widely used operating system for the 1130 was the "Disk Monitor System Version 2" (DM2) introduced in 1967. DM2 is a single-task batch-oriented system. It requires a system with at least 4 KB of core memory and one integrated 2310 disk drive for system residence. The Supervisor is tiny by modern standards, containing assorted system details such as first-level interrupt routines, called "Interrupt Level Subroutines", plus the disk driver and routines to load the interpreter of job control commands and the card reader driver. Device drivers for other I/O devices required by a job are incorporated as part of the loading of that job, which might also include the replacement of the basic disk driver by a more advanced driver. During the execution of a job, only a resident monitor, called the "Skeleton Supervisor", resides in memory. This Supervisor requires just 1020 bytes, so a task's first available memory started with address /01FE (hexadecimal) or word 510. When the job ended or was aborted, the Supervisor loaded the "Monitor Control Record Analyzer" ("MCRA") to read the job control for the next. While the job is running, the Supervisor is inactive. Aside from device drivers and interrupt processing all CPU time is entirely devoted to the job's activities. Other programs distributed as part of the operating system were a core dump utility, "DUMP", and the Disk Utility Program, "DUP".