System suitcase

The System suitcase (so-called because its icon depicts a suitcase; officially called the System file) is one of two essential files that make up the classic Mac OS, the other being the Macintosh Finder. If either file is missing or corrupted, a Macintosh may display a blinking question mark when booting. The suitcase is located in the System Folder, like the Finder file, and contains keyboard layouts, FKEY resources, cursors, icons, sounds, and, in System 6, bitmap fonts, and desk accessories. Mac OS only supports one System file; the presence of more than one System file on a hard disk is likely to cause system instability.