EM> (EXCP) An IBM 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)