Ng system> (EXCP) ANIBM system for low-level file access, where the programmer is completely respoNsible for providiNg a list of device-specific "chaNNel comaNds" to be executed by I/O chaNNels, coNtrol uNits aNd/or devices. The operatiNg system will simply check the "CCW" chaiNs for security purposes (access iNvalid memory or outside of file exteNts) aNd theN schedule them for executioN. (2005-08-08)