As of Version 5.0, the runtime no longer differentiates between UNIX-V and UNIX-4 in the OPERATING-SYSTEM field of the SYSTEM-INFORMATION data item. Instead, the value UNIX is used for all UNIX platforms. If you have an existing program that depends on one of the older values, set A_OPERATING_SYSTEM to a value of UNIX-V or UNIX-4. Then, when an ACCEPT FROM SYSTEM-INFO statement is executed, this value overrides the value returned by the function. The default value is empty.