Cairo would be Microsoft's next-generation operating system based on Windows NT featuring a new user interface and an object-based file system, but it was not planned to be shipped before 1994 (Cairo would never be shipped, however, although elements from the Cairo project would eventually ship in late July 1996 in Windows NT 4.0, without the object-based file system, which would later evolve into WinFS).
But soon into the project, the idea of MS-DOS 7 was abandoned and the decision was made to develop only an integrated graphical OS Windows "Chicago".
The Chicago project was led by Brad Silverberg, who, at that time, was senior vice president of the personal systems division at Microsoft.
Build 58s still included Program Manager as found in Windows 3.1, although this application was supplemented by the new desktop and taskbar/Start menu designs.
This build also introduced shortcuts (Chicago referred to them as Links) and native right click functionality, which Windows 3.1 lacked.