IBM MVS (Multiple Virtual Storage)
IBM MVS was a flagship mainframe operating system that introduced large-scale virtual memory, enterprise batch processing, and high-reliability transaction workloads that still influence modern z/OS systems.
MVS ran on IBM System/370 mainframes and allowed thousands of concurrent jobs using virtual address spaces.
Operators controlled workloads using consoles and 3270 terminals running TSO and ISPF.
Modern descendants of MVS still run banking, airline, and government core systems worldwide.