Submarine Command System SMCS , the Submarine Command System , was first created for the Royal Navy of the United Kingdom ' s Vanguard class submarine s as a tactical information system and a torpedo weapon control system . Versions have now also been installed on all active Royal Navy submarine classes . Initial Phase : SMCS for Vanguard class . With the decision in 1983 to build a new class of submarine to carry the Trident missile system , the UK Ministry of Defence ran an open competition for the command system . Up to that point all RN ships and submarines had command systems built by Ferranti using custom - built electronics and specialised proprietary processors . In a departure from previous practice , which had favoured ' preferred contractor ' policies , the competition was won by a new company called Gresham - CAP , leading a consortium of Gresham - Lion ( now part of Ultra Electronics plc ) and CAP Scientific . The consortium proposed a novel distributed processing system based on Commercial off - the - shelf ( COTS ) processors , with a modular software architecture largely written in the Ada programming language . Each set of Initial Phase SMCS equipment has multiple computer nodes . At the centre of the system there is an Input / Output Node ( which provides interfaces to weapons and sensors ) and a Central Services Node ( which holds fast numeric processors ) . Each central node is duplicated to create a fault - tolerant system which is dual modular redundant . The Human - Computer Interface is provided by Multi Function Consoles and some additional terminals . The dual redundant central nodes are linked to each other and to the consoles via a dual redundant fibre optic LAN . In the Initial Phase equipment fitted to the Vanguard class submarines most processing is done by Intel 80386 single - board computers , each with its own Ada run - time environment . CAP Scientific created a complex layer of middleware to link the many processors together . At its time SMCS was the largest Ada project so far seen . As a pioneering user of Ada , the SMCS project encountered many teething problems with the large - scale use of Ada compilers , Ada development tools , and the special characteristics of the early dialect of the Ada programming language , later known as Ada 83 . Second Phase : SMCS for Swiftsure and Trafalgar class . By 1991 , CAP Scientific was part of Sema Group and the SMCS project was owned by BAeSEMA , a joint venture between Sema Group and British Aerospace . Once SMCS was proven to work on Vanguard boats , it was proposed in the early 1990s to extend its use to the Swiftsure class submarine s and the Trafalgar class submarine s , as part of an improvement programme for these vessels . There was a commercial desire for yet further adoption of COTS technology . The consensus was to port SMCS to some form of UNIX . Sema Group , with considerable experience both of real - time systems and of commercial UNIX , had concerns about the technological feasibility of this port . The essence of the problem was the need to map the Ada tasking environment to the run - time model of UNIX processes in a way which preserved SMCS ' real - time characteristics enough to maintain dependability . A team from BAeSEMA , led by Ray Foulkes , conducted thorough research into possible alternatives to the distributed Ada architecture used in the Initial phase . After extensive investigation of the run - time behaviour of different UNIX variants , and of the code generated by different Ada compilers , the project selected the Solaris operating system running on SPARC computers , which could now be procured as COTS single - board computers . To limit risk , only the consoles were converted to Solaris on SPARC in this phase . The central nodes were kept in the same form as the Initial Phase equipment . The benefit was that there was no need to implement the dual modular redundancy scheme on Solaris at this stage . However , the project had to manage some additional issues arising from mixed intel / SPARC working , such as endianism ( since intel architecture is little - endian and SPARC is big - endian ) . A detailed and generally accurate independent analysis of these stages in the development of SMCS was made in 1998 . Third Phase : ACMS for Astute class . After being successfully deployed on the Swiftsure and Trafalgar submarines in the mixed Intel / SPARC configuration , the architecture was further revised for the UK ' s new attack boats , the Astute class submarine s . The Astute Combat Management System ( ACMS ) combines SMCS with several other sub - systems . For ACMS , the Central Nodes have also been converted to SPARC computers . The dual redundant architecture , both of central nodes and of LAN connections , remains a key feature . There are about twice as many consoles as provided in earlier versions of SMCS . This phase of SMCS is an all - UNIX solution running Solaris on multiple SPARC nodes , with built - in dual redundancy . SMCS - NG ; controversy about system architecture . By 2000 , Sema Group had sold its interest in BAeSEMA , and the SMCS project was now fully owned by BAE Systems . In its last major Defence Review , as reported in 2003 , the UK Parliament agreed numerous improvements for RN submarines , but no changes to the Vanguard boats or the Trident missile system . It was expected that the SMCS equipment , supplied and maintained under a support contract with Ultra Electronics , would last out the service life of the Vanguard fleet . The programmes in place for other submarine improvements were mainly for new sonar equipment , and had been reviewed and approved by the UK ' s parliament . For a brief period , the SMCS project came under the ownership of Alenia Marconi Systems , a joint venture of BAE Systems . In 2002 , it was proposed to convert SMCS to run on standard PC x86 hardware , albeit in rugged industrialised form , for naval command systems . The SMCS project started to develop SMCS - NG ( " Next Generation " ) as SMCS running on PC hardware . The plan was to convert the SMCS infrastructure and applications to run on the Microsoft Windows operating system . However , some software engineers had misgivings . In April 2002 Bill Gates , appearing in his capacity as Microsoft ' s Chief Software Architect , had given sworn testimony under oath to the US Courts . Gates ' testimony included statements that Microsoft Windows was indissoluble and could not be created in cut - down form . Paragraphs 207 to 223 of Gates ' testimony indicated that Windows had an entangled monolithic structure , rather than a structure organised in modular fashion . Assuming Gates ' testimony to be true , these ' pro - UNIX ' engineers felt that open source UNIX rather than Microsoft Windows should be used as the foundation of future naval command systems and circulated their concerns within the company . SMCS - NG as first deployment of " Windows for Warships " . Despite the concerns of some engineers , SMCS - NG was created as a port to Microsoft Windows of the SMCS infrastructure and applications , a move which some commentators have termed " Windows for Warships " . The UK ' s Defence Ministry later gave assurances , through questions in the UK parliament , that this is a low risk use of Microsoft Windows . However , some other suppliers have taken a different path . The consoles for the new Sonar 2076 supplied by Thales Underwater Systems for the Astute class submarines , and which may be retro - fitted to other classes , are built as PCs running Linux rather than Windows . Having developed SMCS - NG as an internal project , BAE Systems independently proposed to the MoD that the original SMCS equipment be replaced by its own , newer , version . After sea trials in HMS " Torbay " , the MoD awarded contracts to BAE Systems for refit of SMCS - NG into most RN submarines , including the Vanguard fleet . Although the Defence Minister Adam Ingram told the UK Parliament in October 2004 that no decision had been made about conversion of the Vanguard fleet to run SMCS - NG , the MoD placed the contracts the following month . By December 2008 , all of the active Royal Navy submarines had been retrofitted with SMCS - NG . Unlike with previous versions of SMCS , the software is supplied as a single - fit release which is intended to be configured for the sensor and weapon fit of each submarine . External links . < br style = " clear : both ; " >