OS/400
OS/400 is the operating system of the AS/400. It is an evolution of the earlier Control Program Facility found on the System/38 and, although the OS/400 branding has been dropped, is still maintained and developed by IBM.
Notable Versions
V2R2 is believed to be the first version of OS/400 to introduce the System Password mechanism.
V3R1 is the first version of OS/400 to add TCP/IP support. It is also one of two versions of OS/400 to receive a simultaneous IPMI and PowerPC AS release; its contemporary PowerPC version was V3R5.
V4R4 is the preferred version of OS/400 to run on first-generation PowerPC AS machines as it is far less demanding on system resources when compared to V5R1, and is the final version of OS/400 to support Advanced/36 and OfficeVision.
V4R5 drops all support for Advanced/36 and OfficeVision, and these applications will be removed when upgrading to V4R5. It is also the final version of OS/400 to not require license keys when installed on an AS/400 Model 150.
V5R1, like its later V5R4 counterpart, was one of the long-toothed releases of OS/400 and could still be found driving many businesses into the 2010s. It is also the final version to be branded OS/400.
