NEC announced ACOS-2 in May 1974 and started shipping it in September of the same year. 　ACOS-2 covered ACOS System models 200 and 250 as an operating system for small computer systems, and its design concept was to meet user needs in the field of small machines or, in other word to satisfy the demand for ease of use. 　Features of its major functions included: (1) Environment for Execution of Various Jobs and High Level of Maintainability A multiprogramming function enabled flexible job execution through combinations of batch processing, communication processing and output writer processing. The OS also had high throughput due to spooling to the printer output. In addition, the OS had a high level of maintainability for elements fundamental to the system, such as the ability to perform system reconfiguration through automatic retry and degeneration by detecting errors due to hardware or software malfunction. (2) Automation/Laborsaving Functions Oriented toward automatic/laborsaving operation, the OS was equipped with functions such as those for automatic power on/off, automatic system startup/stop, automatic execution of reservation operation, job networking, and one-button operation from the operation panel, as well as a data-driven function for linkage between a data medium and a business program. (3) Interactive Processing System PWSS (allowed access to the computer for business operations sites) The PWSS (Personal Work Station System) was capable of selecting and executing a business operation from a workstation and creating a business program in an interactive manner.