LAN Manager
Description
The name Lan Manager was used both for a network layer that was sold as an add on for OS/2 versions 1.x (and could run on later versions) and Unix systems and also a Network Operating System that combined a MicroSoft's or IBM' version of OS/2 server or Hewlett Packard's HP UX and the LAN Manager add on.
Actually the primary developer of the LAN Manager product was 3COM and it was based on a NOS that they had sold under the name 3+Share that used a modified version of DOS called MS-Net as their basis. 3COM lost interest in the product and by 1991 had sold their codebase to MicroSoft who integrated the product into Windows NT Server