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 code clarity, portability, stability and simplicity, making few modifications as possible to software packages from and tries not to anticipate use cases or preclude user decisions. It 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.

Background
The approval of the development of the SAEA information network by the People's Congress in 1959, spurred government investment into computer technology, with various universities, research centers and laboratories working on different projects to bring the network to life. One of these projects led to the creation of the first operating system, the  (Compatible Time-Sharing System) in 1961 led by Francisco J. Corell of Laboratorios Escarzaga.

Most operating systems and programs developed in this period were written in, limiting compatibility between systems as software had to be written specifically for the machine it was meant to operate in. Early were designed to develop specific type of programs, and as such, weren't sufficiently flexible enough to develop a variety of computer programs.

Roberto Solal, a young and gifted computer science and engineering student from the Sierras Technological Institute noticed this, and in 1965 began working on a on his spare time, a project he named the  or U for short. Although originally written in, Solal chose to translate his project into in order to prevent theft by classmates.

Birth
In 1967, Solal became increasingly frustrated with the different operating systems developed for mainframes and, finding them too needlessly complex and inconvenient for programming.

He eventually asked permission to his computer science professor, Héctor Fanti, to use one of the minicomputers in the faculty in order develop his own operating system in assembly. Fanti, aware of Solal's U project, suggested instead to build it on U in order to ensure portability. Solal and Fanti initially worked on the system themselves, but later involved the rest of the faculty in the development process, and chose to name it the Multiplexed Information and Computing Service, or SIIM for short in its Castrian initials.

The project was completed on August 27, 1969, with the system possessing a hierarchical file system, the concepts of computer processes and device files, a command-line interpreter, an assembler, editor, and small utility programs.