Sideways ROMs permitted the addition of new filing systems to the OS (such as the Disc Filing System) and application and utility software. Software supplied as ROMs has two main benefits: it loads instantaneously (if delivered as language or service ROMs), and it requires very little RAM to operate (and may use the dedicated paged ROM area of RAM that normal software keeps clear of). This allowed for application software to have more working space than would normally be possible, and for utility software such as debuggers to operate on software held in RAM.