This category lists operating systems (OSs) based on closed source code. Some such OSs have open source variants (BeOS, DOS, Unix, VMS), or straddle these two licensing models (QNX). Closed Source computer programs, including OSs, are those that include no source code, and for which the source code is kept secret, or made available only for a fee, as in many realtime OSs.
Wherever possible, please submit links about closed source operating systems to extant directory categories on those OSs. Thank you.

IBM

This category holds pointers to directory categories on operating systems (OSs) made by IBM.
This category holds pointers to directory categories on operating systems (OSs) made by IBM.
This category holds pointers to directory categories of Unix operating systems (OSs) that are not open source or free (source code is publicly available), but instead are closed source (source code is kept private and/or secret).
This category holds pointers to directory categories of Unix operating systems (OSs) that are not open source or free (source code is publicly available), but instead are closed source (source code is kept private and/or secret).