This makes the Mac a clean machine, since it has some degree of ROM independence, although certain low-level instructions are invariably kept in ROM. A system upgrade allows old material in ROM to be replaced by new data in the system files.During startup, the information in these files is transferred to the computer’s random access memory (RAM), the main memory of the machine. Some Classic Mac OS instructions are stored in read only memory (ROM), although modern machines keep the majority in the System file, as well as in other files located in the System Folder on the machine’s startup drive. A computer’s operating system (OS) determines its basic behaviour, including responses to instructions and how data is handled in conjunction with a disk drive or a network.
