BS2000 is an operating system for IBM 390-compatible mainframe computers developed in the 1970s by Siemens (Data Processing Department EDV) and from early 2000s onward by Fujitsu Technology Solutions.
Unlike other mainframe systems, BS2000 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.
Currently, it is mainly used in Germany - making up to 83% of its total user base - as well as in the United Kingdom (8%), Belgium (4.8%) and other European countries (4.2%).
BS2000 has its roots in the Time Sharing Operating System (TSOS) 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 I