ReactOS is a free and open-source operating system for amd64/i686 personal computers intended to be binary-compatible with computer programs and device drivers developed for Windows Server 2003 and later versions of Microsoft Windows. ReactOS has been noted as a potential open-source drop-in replacement for Windows and for its information on undocumented Windows APIs.
Former ReactOS project coordinator Aleksey Bragin (left) showing ReactOS to Viktor Alksnis
An operating system (OS) is system software that manages computer hardware and software resources, and provides common services for computer programs.
An IBM System 360/65 Operator's Panel. OS/360 was used on most IBM mainframe computers beginning in 1966, including computers used by the Apollo program.
The first server for the World Wide Web ran on NeXTSTEP, based on BSD.