In the operating system for MELCOM-1530, which was developed in 1963 as a domestically produced model of US TRW’s computer TRW 530, FORTRAN and COBOL compilers, assemblers, a loader, a test support program, SORT/MERGE and a media conversion program were provided as the system programs in order to achieve efficient creation, testing and execution of programs. FORTRAN Monitor that enabled continuous processing of a FORTRAN program from its compilation to execution, and a function for integrating multiple business data processing programs into a single magnetic tape and successively processing the designated programs were also provided.
For MELCOM-3100 announced in 1966, operating systems that systematically organized and enhanced the functions in MELCOM-1530 were provided as its successors. These operating systems (10T, 10PT and 30T) had architecture in which jobs were submitted from paper cards or paper tapes and then compiled and executed using magnetic tapes as the external storage. In addition to the operating system MARK-I and MARK-II which succeeded the above operating systems, the operating system MARK-III which used a magnetic disk as the external storage was also developed for the new models announced in 1968.
In 1970, the MELCOM-7000 series was announced. It was developed as the domestic models of the SIGMA series computers introduced from US SDS (later renamed XDS), with which Mitsubishi Electric had established a technical alliance in order to address TRW’s withdrawal from the computer business. A group of their corresponding operating systems (RBM, BPM, BTM and UTM) provided time-sharing processing, remote batch processing and real-time processing, in addition to formerly used batch processing, and supported these four processing modes simultaneously. The time-sharing processing was particularly distinctive.
For the COSMO series announced in 1974, the newly developed operating system UTS/VS succeeded the operating systems of MELCOM-7000 series, and supported five-dimensional multiplexing through addition of an online transaction processing function. UTS/VS supported a multiple virtual storage and a tightly coupled multiprocessor system.
GOS/VS was the operating system developed for the MELCOM EX series, which was announced in 1985. The maximum number of users, maximum number of terminals and maximum number of connectable devices of GOS/VS were approximately 10 times those of UTS/VS, and new additions included support for dual-processor systems and a function for optimizing use of the computer’s resources. GOS/VS enhanced and strengthened those functions that had been successively introduced from the UTS/VS era, such as network architecture, distributed information processing that combined an online function and a database function, and end-user support and application development based on the Japanese language. In 1990, the GOS/VS operating system was evolved into GOS/EA in order to respond to the expansion of system size and the improvements in system performance by extending the virtual storage area to 256 MB.