The Read-Only Memory (ROM) chips in Macintosh computers store most of the programming routines that make the Macintosh interface so fast and easy-to-use.
For example, the filing system of folders within folders, called Hierarchical Filing System (HFS) provides distinct subdirectories into which applications and documents can be filed. Applications stored in folders can be used from and store files to any other folder. The HFS system also enables the Finder to track file locations and display folder contents quickly.