NEC announced ACOS-4/AVP (Advanced Virtual Processor) in February 1984, and started shipping it in September 1984.
Formerly computers had been used only by certain professionals, but it became the time in which non-professional people used computers for their business. ACOS-4/AVP was developed with the aim of providing greater ease of use for end users, together with more efficient system operation in all fields. ACOS-4/AVP was installed in ACOS System 430, which was hardware designed for downsizing and energy saving in small to medium systems.

 Features of the major functions were as follows:

(1) Increased efficiency in software development with a software support system
SEA/I (Software Engineering Architecture/One), a comprehensive tool covering the whole process of software development from design through production, inspection, maintenance and management, increased efficiency and productivity in software development including standardization of work operations and reuse of resources.
(2) Increased intellectual productivity in office
NEC provided an integrated office system called “Aladdin” to support document/data information processing, communication and decision-making in the office, and to boost individual productivity. In Aladdin, the office environment, including a desk, filing cabinet and trash bin, was represented on screens, and icons for work operations were arranged on the screens to realize user interfaces that visualized deskwork, enabling easy understanding by end users who were not computer professionals.
(3) Provision of numerical values, diagrams, graphs, images, etc.
Based on the Japanese-language information processing system JIPS, the OS was capable of processing information in various forms such as Japanese-language documents, diagrams, images and voices that were more natural and human sounding.
(4) Enhancement of interactive information processing for end users
The OS provided functions that even beginners could use easily by adding commands in menus, a HELP function and a text mail function. In addition, it provided a screen design function and program interfaces to allow end users to build work operations using screens.
(5) Relational database RIQS (Relational Information Query System)
The OS provided the relational database RIQS in addition to the CODASYL-type database ADBS (Advanced Data Base System), which had been provided previously. RIQS data were available from application programs, and RIQS allowed interactive data access through the database service partner TQF (Table-oriented Query Facility), which was a function designed for end users.
(6) Changing from host-centralized processing to distributed processing
As enterprise systems progressed, computers other than host computers, such as office computers and intelligent terminals, were introduced, and data processing tasks were assigned to each computer. The OS facilitated software development in distributed environments by providing the terminal pass-through function TCF, with which users could directly use functions of the host computer, and cross software, which performed part of the host computer processing on office computers or terminals.