OS/2 was originally developed as a combined effort between Microsoft and IBM and first released in 1987.  Both IBM and Microsoft both released versions branded in their own names. OS/2 1.x was a 16-bit OS designed to run on the 80286.

OS/2 Version 1.3 was released in 1991 and it was at this time that Microsoft and IBM split up and went their own directions with the OS. IBM went on to produce IBM OS/2 Version 2, and Microsoft took some of the technology and used it to produce Windows NT.

MS OS/2 booting up. This version was released and branded by Microsoft, so their copyright is everywhere. The versions released by IBM had their copyright everywhere. (Kind of like MS-DOS and IBM PC-DOS did).

No fancy boot screen. Just MS flaunting a couple of their software patents.

The Desktop Manager is kind of like the Windows 3.x program manger, except program groups open in new windows rather than inside the same window. The DOS and Print Manager icons are always present on the desktop as minimized programs. Activating the DOS icons starts a DOS session that can run MS-DOS apps. The print manager is a program that is always running to process print jobs.

The file manager works about the same as the one with Windows 3.0. Drives at the top, directory tree in one window and each folder opens in a window inside the file manage window.

One interesting difference is that each file has many more attributes than an MS-DOS or Windows file, presumably these are stored in the OS/2 "extend attributes" that are included in HPFS or as an add-on to FAT. The files appear to even have their own changeable icon in the attributes.