Features include a menu-driven interface, multi-user support, terminals (IBM 5250) that are (in the grand IBM tradition) incompatible with anything else including the IBM 3270 series, and an extensive library-based operating system, OS/400.
The machine survives because its API layer allows the operating system and application programs to take advantage of advances in hardware without recompilation and which means that a complete system that costs $9000 runs the exact same operating system and software as a $2 million system. There is a 64-bit RISC processor operating system implementation.
It was designed as the successor of the IBM System/38
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