THEOS, which transcribes to "God" in Greek, is an operating system which started out as OASIS, a microcomputer operating system for small computers that use the Z80 processor. Originally written in the late 1970s by Timothy S. Williams as a low-cost alternative to the more expensive mini- and mainframe- computers that were popular in the day, Oasis provided time-sharing multiuser facilities to allow several users to utilise the resources of one computer. Remember that in the 1970s even very basic computers cost many thousands of dollars. THEOS is specifically aimed at small business users.
The language distributed with THEOS was THEOS Multi-User Basic.
When the operating system was launched for the IBM Personal Computer/AT in 1982, the decision was taken to change the name to THEOS, short for THE Operating System. THEOS is under continuous development, and the company is still headed by the founder Tim Williams, who takes a very active role in the product development.
THEOS is used today in Europe, especially in Spain where it was introduced by Fujitsu and other hardware manufacturers 30 years ago. Its latest incarnation is named "THEOS Corona". Corona is a 32/64 bit operating system that targets x86 compatible platforms with popular current market hardware (i.e. SCSI 320, SATA, PCMCIA, USB, PCI/X/64, etc.), particularly high end servers.