Files 442 OSWRSC 443 OSRDSC 443 OSFIND 443 OSGBPB 445 OSBPUT 445 OSBGET 445 OSARGS 445 OSFILE 446 OSRDCH 448 OSASCI 448 OSNEWL 449 OSWRCH 449 OSWORD 449 Command line interpreter (&FFF7) 455 Faults, events and BRK handling 456 Accumulator description 456 Interrupt handling 457 NMI – non-maskable interrupt 457 IRQ – interrupt request 457 45 The operating system calls 442 46 Analogue input 459 Digital input/output using the eight bit user port 460 47 Error messages 462 48 Minimum abbreviations 473 ABS 475 COUNT 475 ELSE 475 EVAL 475 INPUT 476 INSTR 476 ON ERROR 476 OPENIN and OPENUP 476 ASC 477 EQUB, EQUD, EQUS, EQUW 477 OPT 477 49 BASIC II 475