C. Operating System

The Model 91 operates under the IBM-supplied MVT version of OS/360, currently Release 18.6. This system contains a set of modifications developed at CCN for control of batch job flow. MVT is a realization of the general process model of multiprogramming, although this fact is obscured by IBM's terminology. For example, a process is called a task in MVT, while the fork primitive is called "ATTACH".