The Electrical Communication Laboratory (ECL) of Nippon Telegraph and Telephone Public Corporation (now called Nippon Telegraph and Telephone Corporation) set up research and development of a virtual computer (VM: Virtual Machine) system with the aim of improving the efficiency of the task of connecting test processes of software modules in DIPS software development.
In 1976, the company started research and development of a VM control operating system. In 1978, the company released the first version of VM and adopted it for software development at the ECL in Yokosuka.
From 1979 to 1981, the ECL made efforts to improve the performance through such initiatives as adopting the handshake method between a VM monitor and VM OS and achieving command simulation processing in the form of firmware. Success in this resulted in the release of the second version of VM.
From 1984 to 1986, the ECL further improved the performance and increased the coverage of I/O device simulations by adding a VM support function for speeding up processing to the hardware, and the third version of VM was released.
From 1987 to 1991, the company achieved a function for running the VM system in XO mode and a technology for virtualizing a complex computer system. The fourth version of VM was then released.