The latest trend in operating system is the ability to connect with most devices. These is what is known as compatibility of the operating system.
The standard OS for a PC is Windows, and the latest version is Windows 7.
The "latest" OS released by Microsoft is Windows Server 2008. The latest USER operating system is Vista.
Windows 7
Windows 8
version 7
win 8
Win 7
Apple- os x mountain lion is the latest operating system.
Usually referring to the latest version of Microsoft Windows, sometimes to the latest version of OS X.
If by Microsoft you mean the Windows operating system: The latest general OS is Vista (6.0.6002) The latest server OS is Windows Server 2008 (6.0.6002) The latest (release candidate) for Vista's successor is Windows 7 (6.1.7100)
Meaning of open source OS
The 5 "latest" OS's would likely all be various Linux and Unix or BSD based distributions. They update much quicker then windows or mac-os.