The Mark I* at the Armaments Research Development Establishment, Fort Halstead

Fort Halstead in Kent was the first defence establishment to become interested in acquiring a computer, primarily because the UK’s early research into nuclear weapons was carried out there. Ministry of Supply (MOS) priorities were then re-adjusted so that GCHQ got the first Mark I* and the nuclear weapons calculations were transferred temporarily to the Ferranti Mark I at Manchester University. Fort Halstead got its Mark I*, called AMOS, in the summer of 1954. We describe the applications of AMOS over its long and useful life—a life so useful that Fort Halstead decided to build a successor computer in-house that provided a programmers’ interface that had the look and feel of AMOS. The result was COSMOS, about 50 times faster than AMOS. During January 1967 all work was smoothly transferred to COSMOS and AMOS was switched off.