Web site: (not active)
Origin: USA
Desktop environment: CLI
Architecture: IBM 360/370/mainframes
Based on: independent
Wikipedia: 360 and successors
Media: Install
The last version | Released: 2021 (VSE)

DOS/360 (Disk Operating System/360) a first member of a sequence of operating systems for IBM System/360, System/370 and later mainframes, created in 1964.

IBM DOS versions: BOS/360 (Basic Operating System), TOS/360 (Tape Operating System), DOS/360, DOS/VS, DOS/VSE, VSE/AF, SSX/VSE, VSE/SP, VSE/ESA, z/VSE.

Disk and Tape Operating Systems are comprehensive sets of language translators and service programs operating lDlder the supervisory coordination of an integrated control program,. They require an IBM System/360 with at least 16K bytes of main storage .
The disk resident system requires at least one IBM 2311 Disk storage Drive or one IBM 2314 Direct Access Storage Facility.
The tape resident system require sat least f our magnetic tape units. One of the four units, the system residence unit, should be 9-trac k because of the significant system performance advantage it provides. ‘This advantage is most significant during execution of problem-program and language translator functions that require repeated fetching of various program phases. The residence device can be a 7-track mlit with the data convert feature. The IPL routine can determine the physical characteristics of the residence device and perform read backward operations (9-track) or rewind and read forward operations (7-track). The remaining tape units can be either 7- or 9-track.

The IBM System/360 Disk Operating System is designed to handle two types of problem programs: background and foreground. Background programs are initiated by job control from the batched job input stream. Foreground programs are initiated by the operator from the printer-keyboard. A foreground initiator (in lieu of job control) interprets the operator foreground initiation commands.
Foreground programs do not execute from a stack. When one foreground program is completed, the operator must explicitly initiate the next program. The system is capable of concurrently operating one background program and one or two foreground programs. Background and foreground programs initiate and terminate asynchronously from each other. Neither is aware of the other’s existence.
The number of problem program areas (called partitions) and the sizes of the areas are determined by the user initially at system generation time. Each partition is defined as a block of contiguous core storage locations. Although the number and size of the partitions can be redefined subsequently by the operator, the partitions are considered fixed.

All IBM-supplied programs operate only as background programs. These include the language translators (Assembler, COBOL, FORTRAN, PL/I, RPG), the system service programs (librarian, linkage editor), the service programs (sorts, utilities, Autotest), and job control. In addition, Autotest requires a dedicated (no foreground partitions) system.

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