OS/2

OS/2 is an operating system that was originally made by a joint agreement between the Microsoft and IBM companies. The name stands for "Operating System/2". It was intended to replace MS-DOS and Microsoft Windows. OS/2 was maintained by IBM until 2006. 

IBM discontinued its support for OS/2 on 31 December 2006. Since then, it has been updated, maintained and marketed under the name eComStation. In 2015 it was announced that a new OEM distribution of OS/2 would be released that was to be called ArcaOS.

References

Category:Operating systems

OS/2 had true multi-tasking. As a demonstration, ten 1 million line files were each put on display to screen in ten separate windows. On Windows 3.1, only one at a time had display activity. On OS/2, all ten displays moved uninterrupted simultaneously.  IBM LAN Manager also had better measurable performance, being based on an OS/2 server. This was in the early 1990's.I was an OS/2 specialist and IBM LAN Manager Network Administrator with LA DWP,  working there from 1990 to 2015.