BS2000 (renamed BS2000/OSD in 1992) is a mainframe computer operating system developed by Fujitsu Technology Solutions.
Mainframe systems are optimized to enable many programs to be installed in parallel and run concurrently on a computer. This helps reduce the number of computers required to a minimum. Originally this was a way to achieve cost savings, since at that time hardware components were considerably more expensive than now. Today, the advantage of an architecture that gets by with significantly fewer computers is that it greatly reduces the complexity of the IT infrastructure, thus saving on IT running costs and increasing IT robustness.
To avoid different applications and users on a computer adversely affecting one another by contending for resources, mainframe systems must be able to segregate the different users and processes from one another in an optimum manner. They do this by virtualizing all the resources used by the applications and by centralized resource management controlled in a finely graduated way based on access rights and priorities.
At the same time the high degree of virtualization decouples the application software from hardware and implementation details and so creates the foundation for the long-term compatibility, high flexibility, high availability, extensive scalability and great robustness of the services running on mainframes.
Unlike other mainframe systems, BS2000/OSD provides exactly the same user and programming interface in all operating modes (batch, interactive and online transaction processing) and regardless of whether it is running natively or as a guest system in a virtual machine. This uniformity of the user interface and the entire BS2000 software configuration makes administration and automation particularly easy.
Looking back over the history of its development, BS2000/OSD has its roots in the TSOS operating system (TSOS: Time Sharing Operating System) first developed by RCA for the /46 model of the Spectra/70 series, a computer family of the late 1960s related in its architecture to IBM’s /360 series. It was one of the very first operating systems in which the principle of virtual addressing and a segregated address space for the programs of different users was systematically introduced. Right from the outset TSOS also allowed the data peripherals to be accessed only via record- or block-oriented file interfaces, thereby preventing the necessity to implement device dependencies in user programs.
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