When you boot a Macintosh, it makes a startup chime and the screen turns gray. After a few seconds a Happy Mac icon will appear, followed by the splash screen of whatever version of the Mac OS you are running. The Happy Mac indicates booting has successfully begun, whereas a Sad Mac icon indicates a problem in the bootup sequence.
On early Macs that had no internal hard drive, the computer would boot up to a point where it would need to load the operating system from floppy disk. Until the user inserted the correct disk, the Mac would display a blinking disk icon. In actual Macintosh computers, a folder icon with a question mark that repeatedly changes to the Finder icon is shown.
Sources and References
|This page uses Creative Commons Licensed content from Wikipedia. (view authors)|