What does the MSDN, OEM, RTM version of the software mean?

We often hear about the MSDN, OEM, and RTM versions of software, what do they mean, what's the difference?

A MSDN (Microsoft Developer Network) edition

The MSDN software is a software developer-oriented version of Microsoft. MSDN covers all the platforms and applications that can be developed and expanded, such as the Microsoft Encyclopedia Encarta, or a variety of games that are not included in MSDN, because these products are directed toward end users and are not necessary for program development.

(ii) OEM (Original equipment Manufacturer) edition

OEM software can only be shipped with the machine, not retail, so also known as the random version. OEM software can only be installed completely and cannot be upgraded from an old operating system. If you buy a notebook computer or a branded computer, you will have a random version of the software. The packaging is not as exquisite as the retail version, usually with only a piece of CD and instructions (authorization). This system is usually less driven, and the current OEM software is rarely placed on the CD for you to install, either the recovery disk or the hard disk image.

(iii) RTM (release to manufacturing)

Before the software is officially put on the shelves in retail stores, need a period of time to press, packaging, distribution, so the program code must be in the official release a period of time to complete, the completion of the program code is called Final.code, the program code development completed, to send the mother to the factory a large number of presses, this version is called the RTM version. The RTM version of the program code is the same as the official version. But the official version also has a different place: for example, the official version of the OEM can not upgrade the installation, upgrade to a new installation will check the old version of the operating system CD-ROM and so on, these are RTM and the official version of the difference, but their main program code are the same. Strictly speaking, this version still belongs to the FPP Retail edition and needs to be activated.