Complex sentence: Originally, the term stood for "Command file", a text file containing commands to be issued to the operating system, on many of the Digital Equipment Corporation mini and mainframe operating systems going back to the 1970s.
Split into simpler sentences: Originally, the term stood for "Command file" and was a text file containing commands to be issued to the operating system. This was the practice on many of the Digital Equipment Corporation mini and mainframe computer systems going back to the 1970s.