The OKITAC System 9 was developed to be a force in data processing based on the following principles.

  • Better operability on both the hardware and software side
  • Enhanced reliability and maintenance functions
  • Easy construction of multiwork systems
  • Full Japanese language processing functions and graphics processing functions
  • Simplified AP development
  • Continuity for past software assets
  • Software compatibility among all models

CROS (which stood for conversation real-time oriented system) was the operating system for this new OKITAC System 9 series. CROS/D used hard disks as its storage media, whereas CROS/F used floppy disks. Both were real-time multipurpose operating systems with functionality for both operating applications and developing programs.

The features of CROS were as follows.
・High-speed real-time operating systems
The operating systems offered enhanced real-time performance with up to 250 levels of priority control, controls and functions to execute as many as 250 simultaneous tasks, and timer, external interrupt, and other event handling functions.
・Improved man-machine interface
Not only could the programs needed for program development be operated interactively, there was a function for calling as one command a group of commands stored in a file as an alternative to entering operator commands from a terminal.
・Multiwork systems
To provide a more enriched multiwork environment, the operating systems came with multi-terminal control functions, so that multiple users (operators) could work simultaneously on program development or program execution, and functions to verify system usage privileges and file access privileges.
・File operations
The operating systems provided four file access methods — sequential, direct, distributed sequential, and indexed — for effective, flexible support of business process applications without requiring extensive hardware knowledge.
・Japanese language processing
The operating systems came with several programs and dictionaries to support Japanese language processing functions. Japanese was also used for system messages, and COBOL and BPL permitted definitions and input/output of Japanese language data.
・Database management system
In consideration of constructing highly efficient data processing systems, the database management system kept data definitions and reads and writes separate from programs as a way of simplifying updates and extensions.
・Better reliability
The operating systems came with a file restore function, a retry function for input and output devices, and fault troubleshooting and preventative maintenance functions, such as logs, to improve overall system reliability.