IBSYS was the tape based operating system that IBM supplied with its IBM 7090 and IBM 7094 computers. A similar operating system (but with several significant differences), also called IBSYS, was provided with IBM 7040 and IBM 7044 computers.
IBSYS itself was really a basic monitor program, that read control card images placed between the decks of program and data cards of individual jobs. An IBSYS control card began with a "$" in column 1, immediately followed by a Control Name that selected the various IBSYS utility programs needed to setup the and run the job. These card deck images were read from magnetic tapes, prepared offline, not usually directly from the punched card reader.
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