NEC announced ACOS-4/AVP XR (Advanced Virtual Processor eXtended Release) in July 1988, and started shipping it in December 1988.

ACOS-4/AVP XR was an operating system that inherited the design concept of ACOS-4/AVP, which was shipped in 1984, and had enhanced functions for high software productivity, and for establishing an information system by integrating distributed systems, in addition to labor-saving operability and improved ease of operation. It was installed in the small/medium systems ACOS System 3400, announced in July 1988, and its successor ACOS System 3500.

Features of its major functions were as follows:

(1) Highly pursued software productivity
Based on “SEA/I” with further reinforcement of its software development support, the OS provided IDL II and SOFPIA, which achieved a distributed development environment through effective use of an advanced workstation function.
IDL II was a high-level language based on the IDL II language, while SOFPIA was a software development support system based on the COBOL language. These increased the efficiency of development operations mainly in downstream processes, through “visualization” and “automation” approaches based on interactive processing.
(2) Effective use of information in a feeling of personal computer use
The OS provided RIQS II, which achieved high levels of ease of use and flexibility, in a relational database. In addition, it provided a database service partner TQF II and a decision support partner “DS Partner II,” which the end users could use as if they were operating a personal computer, and which allowed them to easily utilize data, from creating a simple report to analyzing advanced management information. In this way, the OS realized effective use of information resources, provision of timely information and improved productivity of the users’ business operations.
(3) Easy integration of distributed systems
The OS facilitated integration of distributed systems by providing a product with specifications based on the distributed system application system DISA. It became possible to establish a horizontal/vertical distributed system due to a high-level network function and a function for centralized operation of a distributed database and a distributed system.