NEC's early hardware consisted of parametron computers (e.g., NEAC-1101) and transistor-based computers (e.g., NEAC-2203).
As software for these early computers, standard routines such as assembler and sorting routines were provided, and the user created software using these standard routines.
Full-scale operating systems (OSs) for NEC’s mainframes were provided from 1964 and consisted of two series: the MOD series and the ACOS, for the corresponding hardware models.
Note: Hereinafter MOD is pronounced as "mode" and ACOS as "eikos."
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MOD I，MOD III，MOD IV，MODVII
OSs MOD I through VII for the NEAC-series 2200, which had compatibility and expandability in data files and application programs based on the one-machine concept, were shipped successively between 1964 and 1970.
MOD Iwas developed for small machines and was available in two types for magnetic-tape systems and disk systems.
MOD III, MOD IV and MOD VII were developed for medium to large machines. They had features such as simultaneous processing of multiple independent programs, dynamic allocation of storage and I/O devices, high-level languages such as COBOL and FORTRAN, a time-sharing system (NEAC-TSS) and CRJE (Conversational Remote Job Entry), and provided a broad range of services according to application operations and the equipment configurations required by users.
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ACOS-2/ACOS-4/ACOS-6
NEC shipped three OS models, OS ACOS-6, ACOS-4 and ACOS-2, for ACOS series mainframes almost at the same time (all announced in 1974), and continued to enhance their functions to meet market demands. In the period up to 1990, NEC commercialized successor OSs ACOS-6/MVX and ACOS-6/MVX II in the ACOS-6 series, which had upper compatibility ("ACOS-6" was also used as the generic name for these systems).
Jointly developed with Toshiba, ACOS-6 provided the advanced multidimensional processing functions (e.g., local batch processing, remote batch processing, transaction processing, TSS) and multiprocessing, making it easy to apply large-scale online systems.
Introduced as an OS for medium-sized machines, ACOS-4 realized seven concepts (high performance, high reliability, larger scale, high operability, high productivity, industrial/international standard and a relational database), and evolved into an OS that had broad expandability to the large-machine area.
ACOS-2 for small machines was equipped with functions and performance equivalent to those of medium to large machines, such as a practical and easy-to-use database, a rich range of end-user facilities, the interactive processing system PWSS (Personal Work Station System) and an automatic operation function, and it was used in a large number of systems because it allowed an online system to be built at low cost.
The OSs provided the following common functions to the user, in addition to OS basic functions that supported hardware characteristics including virtual memory control, multiprocessor control and virtual computer control:
(1) Network function
As the forms of computer networks were changing from direct connection between the computer and terminals to distributed processing, NEC in 1976 announced and achieved a distributed processing oriented network system DINA (Distributed Information-processing Network Architecture). In 1986, this evolved into the communication base DINA-XE (DINA for eXtended Environment), which adopted international standard OSI (Open Systems Interconnection).
(2) Database (DB)
NEC provided a network-type database ADBS (Advanced Data Base System), and built up experience in backbone databases. In addition, NEC shipped RIQS (Relational Information Query System) in the early 1980s, in response to progress in relational database technologies.
(3) Transaction processing system
NEC shipped VIS (Versatile Information System) for ACOS-2/ACOS-4 and TDS (Transaction Driven System) for ACOS-6. They enabled the user to develop an online business program based on COBOL language, which was widely used as a clerical processing language, without having to consider a complex recovery function, database control and communication control, even in developing a large online system.
(4) Program languages and development environment
In addition to the clerical processing language COBOL, scientific engineering computation language FORTRAN and system description language HPL (Higher level Programming Language), NEC shipped IDL II (Integrated Data oriented Language II) as a 4th generation language (aimed at increasing the productivity of business systems) from 1987.
In the CASE (Computer Aided Software Engineering) technical area, NEC in 1983 provided the software development support system SEA/I (Software Engineering Architecture/One), which performed design and automatic synthesis of programs and centralized control of assets in an interactive manner. In 1990, NEC became the first manufacturer to realize client-server type software development support systems SOFPIA (Software Productivity Improvement Aid) and IDLTOOL, which allowed the user to design software on a workstation, and to perform automatic synthesis and asset management using the host computer.