9 DIGITAL COMPUTER SYSTEM, NAMELY CENTRAL PROCESSOR (CENTRAL PROCESSOR MODULE, CONTROL MODULE, MAIN MEMORY AND FLOPPY MAGNETIC DISK UNIT) HARD MAGNETIC DISK UNIT, HARD MAGNETIC DISK UNIT CONTROLLER, [ MAGNETIC TAPE UNIT, MAGNETIC TAPE UNIT CONTROLLER, ] COMMUNICATIONS PROCESSOR, COMMUNICATIONS CONTROLLER, CONSOLE, TERMINAL, PRINTER AND COMPUTER PROGRAMS