MULTIVS

SIIM (Castrian: Servicio de Información e Informática Multiplexada, Multiplexed Information and Computing Service) is a Meralan , originally developed in the 1960s, making it the oldest operating system still maintained.

Initially intended for use inside Merala, the Meralan government licensed SIIM to outside parties in the 70s, spawning the family of operating systems inside the Vastava Pact and its allies, and various open and   systems developed by various countries, such as Temischa, Lyonia and Ziridava which either acquired licenses from the Meralan government, used old versions of Multivs systems as a foundation or simply behave in a manner similar to a Multivs system.

SIIM aims for design stability and simplicity, making few modifications as possible to software packages from and tries not to anticipate use cases or preclude user decisions. provides no graphical installation procedure and no automatic dependency resolution of software packages. It uses plain text files and only a small set of for configuration and administration. Without further modification it boots into a command-line interface environment. The system provides its own, , utilities, and. Because of its many conservative and simplistic features, SIIM is often considered to be most suitable for advanced and technically inclined users.

SIIM distinguishes itself from its predecessors as the first operating system: almost the entire operating system is written in the, which allows SIIM to operate on numerous platforms.