DIPS-103-20OS was developed and released for an online real-time system (RTS) in 1975. The purpose of the 103-20OS development project was to achieve large-scale online processing systems capable of transactional processing tasks, such as online banking operations and online systems of national projects including postal savings operations and the Transportation Ministry’s car registration and social insurance operations, by connecting up to several tens of thousands of terminals operating nationwide to the host computers through communication lines．
Real-time processing is a type of processing in which transactional processing programs are prepared in advance at the host-computer center and data sent from terminals are processed by those programs at the center. Operations such as banking and sales/inventory management are typical examples of jobs that can be processed in RTSs. The real-time operating system 103-20OS was developed to realize such an RTS in DIPS-1.
103-20OS was developed with a total of four layers (with SMP/AP-SMP representing one independent layer): (1) main processing parts consisting of the basic functions of the OS; (2) handling of individual transaction packaged as a real-time processing program; (3) common processes for operation separated into a service/operation management program (SMP/AP-SMP); and (4) service-specific processing configured as an application program.
For real-time processing, real-time specific functions were designed as a package separated from the OS that was clearly defined for basic operating system functions. Later, the OS for a time-sharing system (TSS) and the OS for real-time processing were consolidated and merged into one general purpose OS. The OS for real-time processing remained the base of the new OS, while the functions for TSS were separated and packaged in it.
The first version of 103-21OS was completed and released in March 1975 and was progressively introduced in a number of facilities, including the DRESS Center.