BS2000 (renamed BS2000/OSD in 1992) is a mainframe computer operating system developed by Fujitsu Technology Solutions.
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.
Read more about BS2000: History